ABV
LEGALINDUSTRY
Alcohol by volume — the percentage of a liquid that is pure ethanol. U.S. proof is always exactly double the ABV figure.
Go deeper: Bourbon School →
Bourbon Dictionary
The words behind the whiskey.
Bourbon has its own language. Some of it is law. Some is production shorthand. Some comes from coopers, distillers, blenders, collectors and bartenders. Here's what the words actually mean.
Browse by Subject
Browse by subject
Production: ABV , American Whiskey , Backset , Barrel Entry Proof , Beer Still , Blended Whiskey , Bottling Proof , Bourbon Whiskey , Chill Filtration , Column Still , Congener , Cooper , Cooperage , Corn , Corn Whiskey , Cut , Distillate , Distillation Proof , Distiller's Beer , Doubler , Enzymes , Ester , Ethanol , Family Recipe , Fermentation , Fermenter , Heads , Hearts , House Style , Lincoln County Process , Low Wines , Malted Barley , Mash , Mash Bill , Mash Tun , Neutral Spirits , New Charred Oak , New Make , Pot Still , Proof , Proof Gallon , Proofing , Proofing Down , Rectifier , Rye , Rye Whiskey , Sour Mash , Standards of Identity , Straight Bourbon Whiskey , Straight Whiskey , Sweet Mash , Tails , Tennessee Whiskey , Thumper , TTB , Wheat , Wheat Whiskey , Whiskey , White Dog , Yeast , Yeast Strain
Barrel & Maturation: Aging , Alligator Char , American White Oak , Angel's Share , Barrel Entry Proof , Barrel Finishing , Bonded Warehouse , Bung , Bung Hole , Char , Char Level , Cooper , Cooperage , Evaporation , Extraction , Head , Kiln Drying , Maturation , New Charred Oak , Oxidation , Rackhouse , Red Layer , Rick , Rickhouse , Seasoning , Stave , Temperature Cycling , Toast , Warehouse Position
Bottle & Label: ABV , Age Statement , Barrel Proof , Batch Number , Blended Whiskey , Bonded Warehouse , Bottled in Bond , Bottling Proof , Bourbon Whiskey , Cask Strength , Chill Filtration , Corn Whiskey , DSP , Full Proof , NAS , NCF / Non-Chill Filtered , Proof , Proof Statement , Rye Whiskey , Single Barrel , Small Batch , Standards of Identity , Straight Bourbon Whiskey , Straight Whiskey , Tennessee Whiskey , Wheat Whiskey
Business: Blender , Brand , Contract Distilling , Distiller , Distillery , DSP , Family Recipe , Independent Bottler , Master Distiller , MGP , NDP , Private Label , Producer , Proof Gallon , Provenance , Rectifier , Revived Brand , Sourced Whiskey , TTB
Tasting: Blind Tasting , Congener , Ester , Ethanol , Finish , House Style , Kentucky Hug , Legs , Mouthfeel , Nose , Palate , Proof , Proofing Down , Tannin , Wheater
Collecting: Allocation , Barrel Proof , Batch Number , Bottle Hunting , Cask Strength , Dusty , Honey Barrel , Independent Bottler , Limited Release , MSRP , Private Label , Private Selection , Provenance , Revived Brand , Secondary Market , Single Barrel , Store Pick , Wheater
Cocktails: Amaro , Bitters , Build , Dilution , Modifier , Proof-Forward , Vermouth
Term Family
The Proof Family
Bourbon's proof isn't one number — it's measured, capped, and adjusted at several distinct points. This is where each term in that chain fits.
| Term | Measured | Typical Limit |
|---|---|---|
| Distillation Proof | Off the still | ≤ 160 proof (bourbon) |
| Barrel Entry Proof | Entering the barrel | ≤ 125 proof (bourbon) |
| Barrel Proof / Cask Strength | Bottled as matured, uncut | Varies — whatever the barrel gave |
| Full Proof | Bottled to match original entry proof | Set to entry proof, not barrel proof |
| Bottling Proof | In the finished bottle | ≥ 80 proof (all whiskey) |
Jump to Distillation Proof · Barrel Entry Proof · Barrel Proof · Bottling Proof
A
Age Statement
LEGAL
A label claim stating how long the youngest whiskey in the bottle aged. Legally required only when the whiskey is aged under four years (unless it is Bottled in Bond); optional, and often omitted deliberately, above that.
When a blend combines whiskeys of different ages, the stated age must reflect the youngest component, not an average or the oldest. A producer may understate age but may never overstate it.
Not the same as Aging: "Age" is simply how long a whiskey matured. An "age statement" is the specific legal label claim about that number — a whiskey can have real age without a printed age statement.
Go deeper: Bourbon School → See it in an Issue →
Source: eCFR — 27 CFR § 5.74, Statements of Age, Storage, and Percentage
Aging
INDUSTRY
The time a whiskey spends in a barrel — used interchangeably with "maturation" in most contexts, though "maturation" more precisely emphasizes the changes happening, not just the elapsed time.
Go deeper: Bourbon School → Master Class →
Alligator Char
INDUSTRYSLANG
The nickname for the deepest common char level (#4), whose cracked, blackened surface resembles alligator skin.
Go deeper: Bourbon School → Master Class →
Allocation
INDUSTRY
The limited quantity of a bottle a distillery distributes to a given market or retailer — the mechanism that makes certain releases scarce and hard to find at retail price.
Go deeper: Bourbon School →
Amaro
COCKTAIL
An Italian bittersweet herbal liqueur, increasingly used as a bourbon cocktail modifier for its complex, bitter-forward complexity — a less traditional but increasingly common choice beyond vermouth and bitters.
Go deeper: Bourbon School →
American Whiskey
INDUSTRY
The umbrella term for any whiskey legally produced in the United States — bourbon, rye, wheat whiskey, corn whiskey, malt whiskey, and Tennessee whiskey are all American whiskey categories.
American White Oak
PRODUCTIONINDUSTRY
The oak species (Quercus alba) legally and traditionally used for bourbon barrels, chosen for its tight grain, watertight structure once coopered, and the flavor compounds (vanillin, oak lactones, tannins) heat releases from it.
Go deeper: Master Class →
Angel's Share
INDUSTRY
The whiskey lost to evaporation through the barrel's porous oak during aging — roughly 2-4% of a barrel's volume per year in Kentucky's climate. It concentrates what's left behind rather than simply wasting it.
Go deeper: Bourbon School → Master Class →
B
Backset
PRODUCTION
The acidic spent liquid (stillage) left over after distillation, saved and added to the next mash as part of the sour mash process.
Go deeper: Bourbon School →
Barrel Entry Proof
LEGALPRODUCTION
The proof of the whiskey at the moment it enters the barrel — legally capped at 125 for bourbon. Water and ethanol extract differently from wood, so entry proof is a real production decision, not an afterthought.
Go deeper: Bourbon School → Master Class →
Source: eCFR — 27 CFR § 5.143, Standards of Identity: Whisky
Barrel Finishing
INDUSTRY
Moving fully matured whiskey into a second, different barrel for additional time — a port cask, a second charred oak barrel, a wine cask — to layer on additional wood character after primary aging is complete.
Go deeper: Bourbon School → See it in an Issue →See it in an Issue → Master Class →
Barrel Proof
INDUSTRY
A bottling at whatever proof the whiskey happened to reach after maturation, with no water added to adjust it down. The number varies batch to batch because nobody engineered it.
Not the same as Full Proof: Barrel/Cask Strength means "whatever the barrel gave us, uncut." Full Proof is a specific, different claim: bottled at the whiskey's original barrel-entry proof, which is not necessarily the same as its final matured proof.
Go deeper: Bourbon School → See it in an Issue →
Batch Number
INDUSTRY
A code printed on a bottle identifying which specific production batch it came from — useful for tracking proof, age, or barrel makeup that can vary release to release, especially on small batch or barrel proof lines.
Go deeper: See it in an Issue →
Beer Still
INDUSTRY
The first still in the American whiskey process — a column still that distills distiller's beer into low wines. Named for what goes into it, not what comes out.
Go deeper: Bourbon School →
Bitters
COCKTAIL
A concentrated, highly aromatic flavoring agent used in small dashes to add complexity and balance to a cocktail — the defining ingredient of an Old Fashioned.
Go deeper: Bourbon School →
Blended Whiskey
LEGAL
A mix that combines straight whiskey with other whiskey and/or neutral spirits, as long as the blend is at least 20% straight whiskey by volume. Legally and stylistically distinct from a "blend of straight whiskeys," which contains no neutral spirit at all.
Go deeper: See it in an Issue →
Source: eCFR — 27 CFR § 5.143, Standards of Identity: Whisky
Blender
INDUSTRY
The person responsible for combining barrels — of different ages, recipes, or wood treatments — into a finished, consistent bottled product. A separate skill and role from distilling.
Go deeper: See it in an Issue →
Blind Tasting
TASTING
Tasting a whiskey without knowing its identity, price, or reputation beforehand — a method for reducing the bias that label and price create in a tasting judgment.
Go deeper: Bourbon School →
Bonded Warehouse
LEGALINDUSTRY
A warehouse where spirits are stored under federal supervision before tax is paid — the arrangement that let distillers defer excise tax until the whiskey was withdrawn, and the "bond" in Bottled-in-Bond.
Under the 1897 Act the government supervised the warehouse directly and finished bottles carried federal strip stamps. Those stamps were discontinued at the end of 1982, and the current regulation no longer uses the phrase at all — it requires only that the spirit be stored at least four years in wooden containers. What survives from 1897 is the disclosure, not the lock on the door.
Go deeper: Bourbon School → See it in an Issue →
Bottle Hunting
SLANG
Actively visiting multiple stores in search of allocated, limited, or dusty bottles at retail price rather than paying secondary-market prices.
Bottled in Bond
LEGAL
A federally regulated label meaning the whiskey is the product of one distilling season, one distiller, at one named distillery; aged at least four years in a federally bonded warehouse; and bottled at exactly 100 proof.
The Bottled-in-Bond Act of 1897 was the original law — the first U.S. consumer-protection statute of its kind — but its tax-code provisions were repealed in 1979. The requirements above are today's operative rule, a labeling regulation rather than the original 1897 statute. The designation is also not exclusive to whiskey: current rules permit Bottled-in-Bond rum, brandy and other spirits categories that meet the same core requirements.
Go deeper: Bourbon School →Bourbon School → See it in an Issue →See it in an Issue →
Bottling Proof
LEGALPRODUCTION
The proof of the finished whiskey in the bottle — legally no less than 80 for bourbon. Most bourbon is proofed down with water from its matured barrel strength to a consistent bottling proof.
Go deeper: Bourbon School →
Source: eCFR — 27 CFR § 5.143, Standards of Identity: Whisky
Bourbon Whiskey
LEGAL
Whiskey made in the United States from a grain mash that's at least 51% corn, distilled to no more than 160 proof, entered into a new charred oak container at no more than 125 proof, and bottled at no less than 80 proof, with nothing added but water.
There is no minimum aging requirement to be called bourbon — that higher bar belongs to Straight Bourbon. There is also no legal requirement that bourbon be made in Kentucky; that's concentration of production and tradition, not law.
Not the same as Straight Bourbon Whiskey: Bourbon has no minimum age. Straight Bourbon must age at least 2 years in new charred oak, and if under 4 years, the age must be stated on the label.
Go deeper: Bourbon School →
Source: eCFR — 27 CFR § 5.143, Standards of Identity: Whisky
Brand
INDUSTRY
The name a whiskey is marketed and sold under — which may belong to a distillery, an NDP, or a private label, and does not by itself tell you who actually distilled the liquid inside.
Go deeper: Bourbon School →Bourbon School →Bourbon School → See it in an Issue →See it in an Issue →
Build
COCKTAIL
A cocktail assembled directly in its serving glass (like a Highball or Old Fashioned), as opposed to one stirred or shaken separately and then strained.
Go deeper: Bourbon School → See it in an Issue →
Bung
INDUSTRY
The wooden (or occasionally silicone) stopper that seals the bung hole — the opening used to fill and empty a barrel.
Go deeper: Master Class →
Bung Hole
INDUSTRY
The hole drilled into a barrel stave through which it is filled and emptied, sealed with a bung between fillings.
Go deeper: Master Class →
C
Cask Strength
INDUSTRY
A synonym for Barrel Proof — bottled undiluted, at whatever proof the barrel produced. More common in Scotch terminology, used interchangeably with "barrel proof" in American whiskey.
Go deeper: Bourbon School →
Char
PRODUCTION
The intense, brief flame treatment that carbonizes a barrel's interior surface black — legally required for bourbon's new-oak container. Char creates the burnt outer layer and the heat-altered wood chemistry beneath it that whiskey extracts from for years.
Go deeper: Bourbon School →Bourbon School → See it in an Issue → Master Class →
Char Level
INDUSTRY
A cooperage's shorthand (commonly #1 through #4) for how intensely a barrel's interior was charred. Char number alone doesn't determine flavor — forest origin, seasoning and toast all interact with it too.
Go deeper: Bourbon School → Master Class →
Chill Filtration
INDUSTRY
A cold-temperature filtering step that removes fatty acids and esters to prevent a whiskey from turning cloudy when chilled or diluted. Purely a production/marketing distinction — there is no legal or regulatory definition of chill filtration at all.
Column Still
PRODUCTION
A tall, continuous still — the industry-standard first still for American whiskey — that separates alcohol from the fermented mash through repeated vaporization/condensation across internal plates, running continuously rather than in single batches.
Go deeper: Bourbon School →
Congener
PRODUCTION
Any flavor- or aroma-active compound in a whiskey other than the ethanol and water themselves — esters, higher alcohols, phenols and more. Congeners are what actually give whiskey its character.
Go deeper: Bourbon School → See it in an Issue →
Contract Distilling
INDUSTRY
A distillery producing whiskey specifically for another company to bottle under its own brand name — a standard, openly practiced part of the industry, not a secret.
Go deeper: Bourbon School → See it in an Issue →
Cooper
INDUSTRY
A craftsperson who makes barrels — selecting staves, assembling and hooping them watertight without glue or nails, and toasting or charring the interior.
Go deeper: Master Class →
Cooperage
INDUSTRY
The craft and business of making barrels and other wooden vessels.
In bourbon, cooperage includes selecting and seasoning oak, forming staves, assembling barrels, and toasting and charring them. Because bourbon must mature in new charred oak containers, cooperage has an enormous influence on the final whiskey.
Go deeper: Bourbon School →Bourbon School → Master Class →
Corn
PRODUCTION
Bourbon's required majority grain (minimum 51%). Corn contributes sweetness, body, and a round, grain-forward character — though much of what drinkers taste as bourbon's sweetness actually comes from the barrel, not the corn itself.
Go deeper: Bourbon School → Master Class →
Corn Whiskey
LEGAL
Whiskey made from a mash of at least 80% corn. Unlike bourbon, corn whiskey is not required to be aged in new charred oak — it may be unaged, or aged in used or uncharred containers.
This is a genuinely different rule from bourbon, not a technicality — it is the one common American whiskey category that can legally skip the new-charred-oak requirement entirely.
Source: eCFR — 27 CFR § 5.143, Standards of Identity: Whisky
Cut
PRODUCTIONINDUSTRY
The decision point where a distiller switches from collecting one fraction to the next — from heads to hearts, then hearts to tails. Where exactly to make the cut is a real house-style decision, not a fixed rule.
D
Dilution
COCKTAIL
The water a cocktail picks up from ice during stirring, shaking, or building — a deliberate, necessary part of cocktail construction that softens proof and opens up aroma, not an accident to avoid.
Go deeper: Bourbon School →Bourbon School → See it in an Issue →
Distillate
INDUSTRY
The liquid product of distillation, at any stage — a general term that can refer to low wines, new make, or finished spirit depending on context.
Distillation Proof
LEGALPRODUCTION
The proof of the spirit as it comes off the still, before any water is added. Bourbon must come off the still at no more than 160 proof.
Not the same as Barrel Entry Proof: Distillation proof is measured off the still, before any water is added. Entry proof is measured after water has already been added, right before the spirit goes into the barrel — and it must be lower (max 125) than distillation proof (max 160).
Go deeper: Bourbon School →Bourbon School →
Source: eCFR — 27 CFR § 5.143, Standards of Identity: Whisky
Distiller
INDUSTRY
The person (or, informally, the company) responsible for actually running production — mashing, fermenting, and distilling the whiskey. Distinct from a blender, who works after distillation to combine finished barrels.
Distiller's Beer
PRODUCTIONINDUSTRY
The low-alcohol (roughly 6-10% ABV), unhopped liquid produced by fermentation — the direct input to the still. It genuinely resembles a rough beer, minus hops.
Go deeper: Bourbon School →
Distillery
INDUSTRY
The physical facility where whiskey is actually distilled. A brand and a distillery are not always the same thing — a brand may own its distillery, share one, or use none at all.
Not the same as Producer: A distillery is a physical production facility. A producer is the company selling the whiskey under its brand — which may or may not own the distillery that actually made it.
Go deeper: Bourbon School →
Doubler
INDUSTRY
A second, smaller pot still that redistills the output of the beer still (low wines) to raise proof and refine the spirit before it reaches distillation proof.
Not the same as Thumper: Both are second-distillation vessels doing the same basic job. "Thumper" specifically refers to a version vapor-heated directly from the beer still rather than independently fired — a design detail, not a different process.
DSP
LEGALINDUSTRY
Distilled Spirits Plant — the federal registration number a US facility producing, bottling or warehousing spirits must hold, printed in small text on many labels. A DSP identifies a registered plant, not automatically the one that distilled the contents: depending on the operation and the label wording it may name the bottler instead. It is the best lead on a back label, not proof of origin.
Not the same as Distillery: A DSP is the specific federal permit/number identifying a licensed production facility. "Distillery" is the plain-English word for that same facility — DSP is how you'd verify it on a label.
Go deeper: Bourbon School → See it in an Issue →See it in an Issue →See it in an Issue →
Source: 26 U.S.C. § 5171, Establishment of Distilled Spirits Plants
Dusty
SLANGCOLLECTING
Collector slang for an old bottle found sitting unsold on a store shelf for years — often bottled under a different (sometimes better-regarded) production era or formula than what's currently on shelves.
E
Enzymes
PRODUCTION
Compounds (naturally present in malted barley, or added as commercial products) that break grain starch down into fermentable sugar during mashing, making fermentation possible.
Go deeper: Master Class →
Ester
PRODUCTION
A major family of flavor-active congeners, typically formed when an alcohol and an acid combine during fermentation. Different esters read as fruity, floral, or other distinct aromas depending on which ones a given yeast strain produces.
Go deeper: Bourbon School → See it in an Issue →
Ethanol
TASTINGPRODUCTION
The alcohol itself — the compound proof measures. At high concentration it can register as heat or a sharp, hot sensation that can mask more delicate aromas and flavors.
Go deeper: Bourbon School →
Evaporation
PRODUCTION
The physical loss of liquid through a barrel's porous wood during aging — the mechanism behind the Angel's Share.
Go deeper: Bourbon School → Master Class →
Extraction
PRODUCTION
The process of whiskey pulling color, flavor and tannin compounds out of the barrel wood during maturation — driven by temperature cycling and the whiskey's own proof.
Go deeper: Bourbon School → Master Class →
F
Family Recipe
INDUSTRY
A recipe or production method a distilling family says it has passed down across generations — a claim about lineage and knowledge, not a guarantee that the liquid is chemically identical to what an ancestor once made.
Worth reading the same way as any inherited-yeast claim: the family relationship and the intent to carry something forward are usually verifiable. Whether decades of re-cooking, re-fermenting and re-distilling that recipe produced something flavor-identical to the original is a much harder, often unanswerable claim.
Go deeper: Bourbon School →Bourbon School → See it in an Issue →
Fermentation
PRODUCTION
The step where yeast converts the sugars in a cooked mash into ethanol and CO2, producing a low-alcohol liquid (distiller's beer) ready for distillation — and, along the way, generating the flavor compounds that shape the final whiskey.
Go deeper: Bourbon School →Bourbon School → See it in an Issue →
Fermenter
PRODUCTION
The vessel — traditionally wood, now more often steel — where mash and yeast ferment into distiller's beer over several days.
Go deeper: Bourbon School →
Finish
TASTING
What lingers after swallowing — how long the flavor lasts, and whether it changes character as it fades. One of the three standard stages of tasting, after nose and palate.
Go deeper: Bourbon School →
Full Proof
INDUSTRY
A bottling proofed to match the whiskey's original barrel-entry proof — not simply left undiluted like barrel proof, but deliberately adjusted (up or down) to hit that specific historical number.
Not the same as Barrel Proof: "Full Proof" is a specific, named claim about matching original entry proof. "Barrel Proof" just means nothing was added or removed — whatever proof it naturally reached.
Go deeper: Bourbon School → See it in an Issue →
H
Head
INDUSTRY
The flat circular end piece of a barrel — there are two per barrel, held in place by the hoops, distinct from the curved staves that form the barrel's body.
Go deeper: Master Class →
Heads
PRODUCTIONINDUSTRY
The first, most volatile fraction to come off a still run — typically high in harsh, undesirable compounds like acetone. Distillers cut this fraction away rather than collecting it.
Hearts
PRODUCTIONINDUSTRY
The center fraction of a still run — the cleanest, most desirable spirit — that a distiller collects and carries forward as new-make whiskey. Everything else (heads and tails) is cut away.
Honey Barrel
SLANG
Collector/industry slang for a single barrel that turns out exceptionally well during selection — noticeably better than its siblings from the same batch or warehouse.
Go deeper: Bourbon School →
House Style
INDUSTRY
The recognizable flavor signature a distillery aims for across its whole lineup — the product of its specific mash bills, yeast, stills, barrel program and blending choices working together, generation after generation.
Go deeper: Bourbon School → See it in an Issue →
I
Independent Bottler
INDUSTRY
A company that buys aged whiskey (usually barrel by barrel) from distilleries and bottles it under its own label, distinct from an NDP that typically buys and blends larger bulk lots.
Go deeper: Bourbon School →
K
Kentucky Hug
SLANG
Enthusiast slang for the warm, enveloping sensation a higher-proof bourbon produces in the chest after swallowing.
Go deeper: Bourbon School →
Kiln Drying
INDUSTRY
An accelerated, artificial alternative (or supplement) to outdoor air seasoning — drying staves in a heated kiln rather than letting weather do the work over months or years.
Go deeper: Master Class →
L
Legs
TASTINGSLANG
The streaks of liquid that run down the inside of a glass after swirling — caused by alcohol evaporating faster than water. A visual curiosity more than a reliable indicator of quality or age.
Limited Release
INDUSTRY
A bottling produced in a restricted, one-time or infrequent quantity — as opposed to a brand's standard, always-available core lineup.
Go deeper: Bourbon School →
Lincoln County Process
INDUSTRY
Filtering new-make whiskey through a bed of maple charcoal before it enters the barrel — the defining production step that distinguishes Tennessee Whiskey from bourbon.
Low Wines
INDUSTRY
The lower-proof spirit produced by the first (beer still) distillation, still needing a second distillation before it reaches bourbon's legal distillation-proof range.
M
Malted Barley
PRODUCTION
Barley that's been germinated and dried, present in nearly every bourbon mash bill in small amounts (roughly 4-15%). Its enzymes convert starch into fermentable sugar, and it contributes its own bready, biscuity flavor on top of that job.
Go deeper: Bourbon School → Master Class →
Mash
PRODUCTION
The cooked mixture of grain and water, before or during fermentation. The word describes the physical batch itself, not the grain ratio recipe — that's the mash bill.
Not the same as Mash Bill: The mash is the physical cooked batch. The mash bill is the grain-ratio recipe used to make it — the difference between the dish and the recipe.
Go deeper: Bourbon School →
Mash Bill
PRODUCTIONINDUSTRY
The grain recipe behind a whiskey — the specific percentages of corn, rye or wheat, and malted barley used in the mash. Bourbon's mash bill must be at least 51% corn.
Not the same as Mash: A mash bill is the recipe (percentages of each grain). A mash is the actual cooked, wet batch of grain and water made from that recipe.
Go deeper: Bourbon School → See it in an Issue → Master Class →
Mash Tun
PRODUCTION
The vessel where grain is cooked with water to convert starch into fermentable sugar, before the mash is transferred to a fermenter.
Go deeper: Bourbon School →
Master Distiller
INDUSTRY
A distillery's senior production authority — the person responsible for the recipes, the fermentation and distillation decisions, and ultimately the finished flavor of everything the company makes. An informal industry title, not a licensed credential.
A Master Distiller title tells you who ran production, not who owns the company. The same family can hold the Master Distiller role at one distillery generation after generation while a completely different family or company owns the business the whole time — see Issue No. 010 for a working example.
Not the same as Producer: A Master Distiller is a production role — a job a person holds. A producer is the company that owns the brand. One family can supply a company's Master Distillers for generations without that family ever owning the company itself.
Go deeper: Bourbon School → See it in an Issue →
Maturation
PRODUCTIONINDUSTRY
The process of a whiskey changing over time in the barrel — extracting color and flavor from the wood, losing volume to evaporation, and being shaped by temperature and warehouse position.
Not the same as Aging: These are effectively synonyms in everyday use. If there's a nuance, "aging" leans toward simply describing elapsed time; "maturation" emphasizes the chemical and physical changes happening during that time — but most people, including distillers, use them interchangeably.
Go deeper: Bourbon School →Bourbon School → Master Class →
MGP
INDUSTRY
Midwest Grain Products — a large Indiana distillery whose whiskey has appeared under many separate brand names over the years, making it the most commonly cited example of contract distilling in American whiskey.
Go deeper: Bourbon School →
Modifier
COCKTAIL
A cocktail ingredient (vermouth, amaro, liqueur) that adjusts and complements the base spirit's character, rather than serving as the primary flavor itself.
Go deeper: Bourbon School → See it in an Issue →
Mouthfeel
TASTING
The physical, textural sensation of a whiskey in the mouth — viscous or thin, oily or watery, warming or sharp — distinct from its actual flavors.
Go deeper: Bourbon School →
MSRP
INDUSTRY
Manufacturer's Suggested Retail Price — the producer's published target price, which allocated or hyped bottles frequently sell well above on the shelf or secondary market.
Go deeper: Bourbon School →
N
NAS
INDUSTRY
No Age Statement — a bottle that makes no legal age claim on its label. NAS does not mean young; it means the producer chose not to (or legally cannot) commit to a specific number.
Go deeper: Bourbon School → See it in an Issue →
NCF / Non-Chill Filtered
INDUSTRY
Whiskey bottled without chill filtration — a process that would otherwise strip out fatty acids and esters that can cloud the liquid at low temperature or high proof. NCF preserves those compounds, which some drinkers believe adds texture and flavor.
Go deeper: See it in an Issue →
NDP
INDUSTRY
Non-Distiller Producer — a company that sells whiskey it bought from another distillery rather than distilling itself. Not automatically a red flag; it's how many respected brands built their business while their own distillery and stocks matured.
Not the same as Sourced Whiskey: NDP describes the type of company (one that doesn't distill). "Sourced whiskey" describes the liquid itself (bought from elsewhere). An NDP's whole lineup is sourced whiskey; a distillery that occasionally buys extra stock also has some sourced whiskey without being an NDP.
Go deeper: Bourbon School → See it in an Issue →See it in an Issue →See it in an Issue →
Neutral Spirits
LEGAL
Distilled spirits produced at or above 190 proof, so highly rectified they carry essentially no flavor from the grain they were made from — the base of most vodka, and a legal ingredient in some blended whiskeys.
Source: eCFR — 27 CFR § 5.143, Standards of Identity: Whisky
New Charred Oak
LEGAL
The legally required container for bourbon: a barrel made of new (never before used) oak, with its interior charred. Every bourbon barrel is used exactly once for bourbon, by law.
Go deeper: Bourbon School → Master Class →
Source: eCFR — 27 CFR § 5.143, Standards of Identity: Whisky
New Make
PRODUCTIONINDUSTRY
Whiskey immediately after distillation, before it enters a barrel — clear, unaged, and legally not yet 'whiskey' in some contexts until it's touched wood.
Not the same as White Dog: These are true synonyms — "new make" is the more technical/industry term, "white dog" the more folksy American one. Both mean unaged spirit straight off the still.
Go deeper: Bourbon School →
Nose
TASTING
The aroma of a whiskey, smelled before tasting — often the source of most of what registers as 'flavor' in the mouth. Also used as a verb: to nose a whiskey.
Go deeper: Bourbon School →
O
Oxidation
PRODUCTION
Chemical changes in whiskey caused by exposure to oxygen during long maturation — distinct from extraction (pulling compounds from wood), though the two happen together and both shape a whiskey's character over years.
Go deeper: Bourbon School → Master Class →
P
Palate
TASTING
The flavors and sensations experienced in the mouth once whiskey is tasted — sweetness, spice, fruit, oak, body — as distinct from the nose (aroma) and finish (aftertaste).
Go deeper: Bourbon School →
Pot Still
PRODUCTION
A traditional batch still — a single heated pot that distills one batch at a time. Some American whiskey producers use a pot still for a second distillation after an initial column-still run, or exclusively for a more traditional, hands-on style.
Go deeper: See it in an Issue →
Private Label
INDUSTRY
A whiskey bottled under a retailer's or restaurant's own brand name rather than a distiller's or NDP's name — the liquid is sourced, but the labeling is exclusive to that buyer.
Private Selection
INDUSTRY
A distillery's formal program allowing a retailer, bar, or private group to select and purchase their own single barrel — the branded version of what's generically called a 'store pick.'
Go deeper: Bourbon School →
Producer
INDUSTRY
The company that owns and sells a whiskey brand — which may or may not distill it themselves. All distilleries are producers of their own whiskey; not all producers are distilleries.
Go deeper: Bourbon School →
Proof
LEGALINDUSTRY
A measure of a spirit's alcohol strength. In the U.S., proof is exactly twice the alcohol-by-volume percentage — a whiskey at 45% ABV is 90 proof.
Go deeper: Bourbon School →
Proof Gallon
LEGAL
The federal tax unit for distilled spirits: one gallon of spirit at exactly 100 proof, or the volume-adjusted equivalent at any other proof. Federal excise tax is calculated per proof gallon, not per gallon of liquid.
Proof Statement
INDUSTRY
The label declaration of a spirit's proof and/or ABV. Unlike an age statement, which is only required below four years old, mandatory alcohol-content labeling applies to distilled spirits generally.
Proof-Forward
COCKTAILSLANG
A cocktail style that deliberately uses a higher-proof spirit and minimal dilution, so the drink stays spirit-forward rather than getting softened toward the modifiers.
Go deeper: Bourbon School →
Proofing
PRODUCTION
The act of adding water to a spirit to adjust it to a target proof — done at multiple stages: before barrel entry, and again before bottling.
Go deeper: Bourbon School →
Proofing Down
PRODUCTION
Diluting a matured, higher-proof whiskey with water to reach its final bottling proof — the opposite choice from a barrel-proof release, which skips this step entirely.
Go deeper: Bourbon School →
Provenance
INDUSTRY
The documented chain of where a whiskey was distilled, aged, blended, bottled and owned. A provenance claim is a claim about that chain — and naming a famous distillery is not the same as proving the liquid came from it.
Go deeper: Bourbon School →Bourbon School →Bourbon School → See it in an Issue →
R
Rackhouse
INDUSTRY
A synonym for rickhouse — the warehouse where filled bourbon barrels age. Which word a distillery uses is house style, not a functional difference.
Go deeper: Bourbon School → Master Class →
Rectifier
INDUSTRY
A historical middleman who bought whiskey or neutral spirit in bulk and prepared it for sale — blending it, adjusting its strength, and often colouring and flavouring it — then sold the result under his own branding.
Rectifying was legal and widespread through the 19th century, and much of it was skilled blending. The problem was disclosure: nothing required a rectifier to say what he had done. The Bottled-in-Bond Act of 1897, the Pure Food and Drug Act of 1906 and the 1909 Taft Decision are all responses to that gap, and the modern non-distiller producer is the rectifier's regulated descendant.
Not the same as NDP: Both sell whiskey they didn't distill. A 19th-century rectifier could alter it and say nothing about it; a modern NDP must disclose where the whiskey was distilled and bottled.
Go deeper: Bourbon School →Bourbon School → See it in an Issue →
Red Layer
INDUSTRY
The reddish-brown, heavily heat-altered layer of wood sitting just beneath a barrel's carbonized black char surface — one of several distinct layers whiskey interacts with across years of aging, not just the black surface itself.
Go deeper: Bourbon School → Master Class →
Revived Brand
INDUSTRY
A whiskey name brought back into use by a company with no necessary connection to the original business — usually by registering a trademark that lapsed after the first owner failed or walked away.
Trademarks are cheap to hold and distilleries are expensive to run, so names routinely outlive the plants that made them. A heritage date on a revived brand may describe a distillery, a family, or a name's first use. It rarely describes the company selling the bottle, and it never describes the liquid, which was distilled recently somewhere identifiable.
Not the same as Brand: Every revived brand is a brand. What makes it revived is the break — a period when nobody was using the name, after which someone unconnected to the original owner picked it up.
Go deeper: Bourbon School → See it in an Issue →See it in an Issue →
Rick
INDUSTRY
A wooden rack structure inside a traditional rickhouse that barrels are stacked on, several tiers high — the structure the building is named for.
Go deeper: Bourbon School → Master Class →
Rickhouse
INDUSTRY
A warehouse where filled barrels age — named for the wooden ricks (racks) traditionally used to stack them. Temperature, humidity and a barrel's specific floor and position all shape how it matures.
Not the same as Rackhouse: True synonyms — regional/house-style preference, not a functional difference. Both mean the aging warehouse.
Go deeper: Bourbon School → Master Class →
Rye
PRODUCTION
The traditional secondary grain in bourbon, added for spice, pepper, and a drier finish. A whiskey with rye as its majority grain (51%+) is legally Rye Whiskey, not bourbon.
Go deeper: Bourbon School → See it in an Issue → Master Class →
Rye Whiskey
LEGAL
A legally distinct whiskey made from a mash of at least 51% rye, aged in new charred oak, otherwise following the same proof rules as bourbon (max 160 proof off the still, max 125 entry proof, min 80 bottling proof).
Go deeper: Bourbon School →
Source: eCFR — 27 CFR § 5.143, Standards of Identity: Whisky
S
Seasoning
PRODUCTIONINDUSTRY
The period — often outdoors, sometimes a year or longer — that cut oak staves spend exposed to air and weather before cooperage. Seasoning breaks down harsh wood compounds and softens tannins before the wood is ever toasted or charred.
Go deeper: Master Class →
Secondary Market
INDUSTRYSLANG
The (in most U.S. states, legally gray or outright illegal without a liquor license) resale market where allocated or discontinued bottles trade well above retail price.
Go deeper: Bourbon School →
Single Barrel
INDUSTRY
Whiskey bottled from one specific barrel, not blended with any others — meaning genuine barrel-to-barrel variation is part of the product, not a flaw.
Not the same as Small Batch: Single Barrel comes from exactly one barrel. Small Batch blends a deliberately limited number of barrels together — more than one, fewer than a full standard blend. Neither term has a legal definition.
Go deeper: Bourbon School → See it in an Issue →See it in an Issue →
Small Batch
INDUSTRY
A blend from a smaller, deliberately chosen number of barrels rather than a brand's full standard-lineup blend. No legal definition governs how small "small" has to be.
Go deeper: Bourbon School → See it in an Issue →See it in an Issue →See it in an Issue →
Sour Mash
PRODUCTIONINDUSTRY
A fermentation method where each new batch is inoculated with a portion of stillage (backset) from a previous batch. It stabilizes pH and keeps a distillery's house flavor consistent — most American whiskey is made this way, whether or not it says so.
Not the same as Sweet Mash: Sour mash uses backset from a prior fermentation to set pH. Sweet mash uses none — each batch starts fresh. Sour mash is the industry default; sweet mash is the exception.
Go deeper: Bourbon School →
Sourced Whiskey
INDUSTRY
Whiskey that a brand bought, in bulk, from another distillery rather than making itself. Describes the liquid's origin — distinct from NDP, which describes the type of company selling it.
Go deeper: Bourbon School → See it in an Issue →See it in an Issue →See it in an Issue →
Standards of Identity
LEGAL
The section of federal regulation (27 CFR Part 5) that legally defines every distilled spirits category — bourbon, rye, gin, vodka and the rest — including exactly what production steps a producer must follow to use each name.
Go deeper: Bourbon School →
Source: eCFR — 27 CFR § 5.143, Standards of Identity: Whisky
Stave
INDUSTRY
One of the individual curved wood planks that, hooped together, form the body of a barrel.
Go deeper: Master Class →
Store Pick
INDUSTRYCOLLECTING
A single barrel selected by a retailer or bar rather than the distillery itself — the same basic idea as a distillery-chosen Single Barrel, just with the choice made downstream.
Not the same as Private Selection: These are effectively the same practice under different brand vocabulary — some distilleries call their retailer/bar-selection program "Private Selection," others just get called "store picks" generically. Not a meaningful functional difference.
Go deeper: Bourbon School → See it in an Issue →
Straight Bourbon Whiskey
LEGAL
Bourbon that has aged at least two years in new charred oak containers. If a Straight Bourbon is aged less than four years, federal rules require an age statement on the label.
Not the same as Bourbon Whiskey: Every Straight Bourbon is a Bourbon Whiskey. Not every Bourbon Whiskey has aged long enough, or been labeled correctly, to legally call itself "Straight."
Go deeper: Bourbon School →Bourbon School →
Source: eCFR — 27 CFR § 5.143, Standards of Identity: Whisky
Straight Whiskey
LEGAL
Whiskey (of any grain type — bourbon, rye, wheat, malt) aged at least two years in new charred oak, with no coloring, flavoring, or blending materials added.
Source: eCFR — 27 CFR § 5.143, Standards of Identity: Whisky
Sweet Mash
PRODUCTION
A fermentation method that uses no backset — every batch starts with fresh water and fresh yeast rather than inheriting acidity from a prior batch. Rarer today than sour mash, but still used by some distillers for a different, less acidic profile.
Go deeper: Bourbon School →
T
Tails
PRODUCTIONINDUSTRY
The final fraction of a still run, coming off as proof drops — heavier, oilier, and less desirable. Cut away like heads, sometimes redistilled in a future run rather than discarded outright.
Tannin
TASTINGPRODUCTION
A class of compounds extracted from oak during maturation, contributing dryness, structure, and an astringent edge — especially pronounced in whiskeys that have aged a very long time.
Go deeper: Bourbon School →Bourbon School → Master Class →
Temperature Cycling
PRODUCTION
The seasonal expansion and contraction of a barrel's wood as warehouse temperature rises and falls — pushing whiskey into the wood in warm weather and pulling it back out as it cools, which drives extraction over years of aging.
Go deeper: Bourbon School → Master Class →
Tennessee Whiskey
LEGALINDUSTRY
Whiskey that meets bourbon's legal requirements, is produced in Tennessee, and (with one grandfathered exception) is filtered through a layer of maple charcoal — the Lincoln County Process — before barreling.
Tennessee Whiskey is essentially bourbon by every technical requirement, but the Lincoln County Process step and the Tennessee-production rule are why producers and law don't simply call it bourbon.
Source: eCFR — 27 CFR § 5.143, Standards of Identity: Whisky
Thumper
INDUSTRYSLANG
A doubler-style second still heated by vapor piped directly from the beer still, rather than having its own independent heat source — named for the thumping sound the vapor makes passing through the liquid inside it.
Toast
PRODUCTIONINDUSTRY
A lower-intensity, longer-duration heat treatment applied to a barrel's interior — distinct from char. Toasting tunes the wood's chemistry (caramelized, spice-driven compounds) without carbonizing the surface black.
Not the same as Char: Toast is lower heat applied longer, leaving brown wood. Char is intense flame applied briefly, carbonizing the surface black. They are different heat treatments, not two intensities of the same fire — and bourbon's new-oak barrel legally requires char, not toast.
Go deeper: Bourbon School → See it in an Issue → Master Class →
TTB
LEGAL
The Alcohol and Tobacco Tax and Trade Bureau — the U.S. Treasury agency that writes and enforces the federal rules defining bourbon, straight whiskey, Bottled-in-Bond, and every other legally defined spirits category.
Source: TTB.gov
V
Vermouth
COCKTAIL
A fortified, aromatized wine used as a cocktail modifier — the defining ingredient of a Manhattan, adding sweetness, herbal complexity, and dilution to a bourbon-based stirred drink.
Go deeper: Bourbon School →
W
Warehouse Position
INDUSTRY
Where a specific barrel sits inside a rickhouse — which floor, and where on that floor. Hotter top floors and cooler bottom floors mature whiskey differently, so two barrels filled the same day can taste meaningfully different years later based on position alone.
Go deeper: Bourbon School → Master Class →
Wheat
PRODUCTION
A secondary grain some distillers swap in for rye to soften the whiskey — less pepper and heat, more perceived sweetness and roundness. The basis of the 'wheated bourbon' style.
Go deeper: Bourbon School → See it in an Issue →See it in an Issue → Master Class →
Wheat Whiskey
LEGAL
Whiskey made from a mash of at least 51% wheat, aged in new charred oak — legally distinct from a wheated bourbon, which is still corn-majority with wheat as the flavor grain.
Not the same as Wheat: Wheat Whiskey is a legal category (wheat is the majority grain). A "wheated bourbon" is still legally bourbon (corn-majority) with wheat as its secondary flavor grain.
Go deeper: Bourbon School →
Source: eCFR — 27 CFR § 5.143, Standards of Identity: Whisky
Wheater
SLANG
Enthusiast shorthand for a wheated bourbon — one that uses wheat instead of rye as its secondary grain.
Go deeper: Bourbon School → See it in an Issue →
Whiskey
LEGALINDUSTRY
A spirit distilled from a fermented grain mash and matured in wood. "Whiskey" (or "whisky" outside the U.S. and Canada) is the broad legal and common-use category that bourbon, rye, Scotch, and Irish whiskey all belong to.
Go deeper: Bourbon School →
Source: eCFR — 27 CFR § 5.143, Standards of Identity: Whisky
White Dog
INDUSTRYSLANG
The American-vernacular term for new-make whiskey — clear, unaged spirit fresh off the still, before it ever sees a barrel.
Go deeper: Bourbon School →
Y
Yeast
PRODUCTION
The microorganism that converts fermentable sugar into alcohol and carbon dioxide. Different yeast strains produce different flavor-active byproducts, making yeast a real, deliberate flavor variable — not just a mechanical step.
Go deeper: Bourbon School → See it in an Issue →See it in an Issue →
Yeast Strain
PRODUCTION
A specific, genetically distinct population of yeast — the thing a distillery actually means when it says it uses "proprietary yeast." Different strains produce different flavor-active byproducts even from an identical mash.
A strain is not the same claim as a yeast culture that has been kept alive and propagated for decades, or a century-old strain "recovered" from a dormant sample — see the confused-with note below before treating any of those three claims as interchangeable.
Not the same as Yeast: Yeast is the organism generally. A strain is one specific, genetically distinct population of it — the level of precision a distillery is actually making a claim about when it says its yeast is "proprietary" or "original."
Go deeper: Bourbon School →Bourbon School → See it in an Issue →See it in an Issue →