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Gambling Glossary: Casino & Sports Betting Terms

Plain-English definitions of the most important gambling terms across casino games, slots and sports betting – with a focus on odds, house edge, risk and bankroll management.

How to use this page:
Skim by letter, or use your browser’s search (Ctrl+F / Cmd+F) to jump straight to any term. Wherever it helps, we link to deeper guides on odds, EV, bankrolls and house edge.
A B C D E F G H J K L M N O P R S T U V W

This glossary doesn’t try to list every obscure term ever used. Instead, it focuses on words that affect your odds, risk, expectations and behaviour when you gamble – the parts that matter most for your wallet and mental health.

Casino Sports Betting Math of Gambling Psychology

A

  • Action
    Total amount of money you’re betting over time. A “lot of action” means many bets or high stakes, not just a single big wager. More action = more exposure to the house edge.
  • Advantage Player (AP)
    Someone who looks for situations where they have a genuine mathematical edge over the house or other players (for example, specific promotions, some forms of poker, or expert-level card counting in blackjack). Most casual players are not APs and should assume the house has the edge.
  • Against the Spread (ATS)
    In sports betting, wagering on a team with the point spread factored in (e.g., -3.5). The bet is graded on whether they “cover” that spread, not just who wins straight up. See also Moneyline, Spread & Totals when that guide is live.
  • All-In
    In poker, betting all of your remaining chips. In a broader sense, people sometimes use “all-in” for risking their entire bankroll, which is not recommended in real-money gambling.

B

  • Bankroll
    The total amount of money you’ve set aside purely for gambling. Good practice is to keep it separate from everyday money (bills, rent, groceries) and manage it with a plan – see Bankroll Management for Beginners.
  • Bankroll Management
    The set of rules you use to decide how much to bet, how long to play, and when to stop. Proper bankroll management reduces your risk of ruin and makes it less likely that one bad night wipes you out. Covered in detail in our bankroll guide.
  • Bonus
    Extra funds or free bets offered by casinos and sportsbooks to attract or retain players. Every bonus comes with terms (wagering requirements, game restrictions, time limits) that you should read carefully before opting in.
  • Bonus Abuse
    Trying to exploit bonuses in ways that break a site’s terms (e.g., multiple accounts, collusion). This can lead to confiscated winnings or closed accounts. For regular players, the key is simply to follow the rules and understand that bonuses are designed to maintain a house edge, not give you a guaranteed profit.
  • Break-Even Percentage
    The win rate you need to neither gain nor lose money at given odds. For example, at -110 American odds, you must win about 52.4% of the time to break even. See Odds Explained and Expected Value.

C

  • Cashback
    A promotion where the casino returns a small percentage of your losses over a period as bonus money or cash. Nice to have, but it doesn’t remove the house edge.
  • Chasing Losses
    Increasing bet sizes or continuing to play after hitting your loss limit, in an attempt to “get even.” This is a major red flag for tilt and problem gambling – see Tilt Control & Session Rules and Responsible Gambling.
  • Comps (Complimentary)
    Rewards given by casinos (online or land-based) such as free spins, meals, hotel nights or cashback. They’re a form of loyalty program funded by the house edge in your play – not free money in the long run.
  • Craps – Come-Out Roll
    The first roll in a round of craps. It determines whether you win immediately on bets like Pass Line, lose immediately, or establish a point. Our craps guide on Gambling101 explains low-edge bets vs sucker bets when that section is live.

D

  • Decimal Odds
    An odds format popular in Europe and online sportsbooks. The number represents total return per 1 unit stake, including your original stake. For example, 2.50 means a $10 bet returns $25 total. See Odds Explained: American, Decimal, Fractional.
  • Dog (Underdog)
    In sports betting, the team or player expected to lose. Often shown with positive American odds (e.g., +150). Underdogs lose more often but pay more when they win.
  • Double or Nothing
    A bet where you either double your current amount or lose it. Commonly used when people chase losses (“I’ll just double this one and quit”), which is risky and often leads to bigger losses when combined with the gambler’s fallacy.

E

  • Edge
    The mathematical advantage one side has over the other. The house edge is the casino’s advantage; in some cases, skilled players can gain an edge over opponents or promotions, but this is rare for casual gamblers. See House Edge by Game.
  • EV (Expected Value)
    The long-run average result of a bet if you could repeat it many times. A negative EV means you’re expected to lose on average; a positive EV means profit in the long run. Our EV guide shows how to calculate it in practice.

F

  • Favourite
    In sports betting, the team or player expected to win. Often shown with negative American odds (e.g., -150). Favourites win more often but pay less when they do.
  • Free Spins
    Slot spins provided by the casino as part of a promotion or in-game feature. They can still be subject to wagering requirements or capped winnings – always read the terms before assuming they’re “pure profit.”

G

  • Gambler’s Fallacy
    The mistaken belief that past outcomes influence future ones in independent games (“Red has hit five times, so black is due”). This bias leads to bad decisions and chasing losses. See Gambler’s Fallacy Explained.
  • Grind
    Playing many small, relatively low-risk bets over a long period, often aiming to slowly clear bonuses or earn comps. It still exposes you to the house edge over time.

H

  • Hand
    A single round of play in card games like blackjack or poker. Each hand has its own probabilities and EV depending on rules and your decisions.
  • High Roller
    A player who wagers large amounts. High rollers may receive special comps or VIP treatment, but they also face large swings in results and greater risk if bankroll management is poor.
  • House Edge
    The built-in advantage the casino has in a game, usually expressed as a percentage of each bet. For example, a 1% edge means the casino expects to keep about $1 per $100 wagered over the long term. See House Edge by Game and EV for Gamblers.

J

  • Jackpot
    The top prize available on a game (often a slot or certain table side bets). It can be fixed (same amount) or progressive (grows over time as players wager).

K

  • Kelly Criterion
    A formula for sizing bets when you believe you have a real edge, balancing growth and risk of ruin. In practice, most recreational players are better off with simpler, conservative staking rules. See Kelly Criterion – Lite Version.

L

  • Line (Betting Line)
    The odds and/or point spread offered on a sports event. “Line shopping” means comparing lines across different sportsbooks to find better prices – covered in our sports betting guides when live.
  • Live Dealer
    Online casino games where a real dealer is streamed by video, and you bet remotely. The outcome is determined by physical cards or wheels, not RNG, but the same house edge and bankroll principles apply.

M

  • Martingale
    A betting system where you double your stake after every loss until you win. It relies on the gambler’s fallacy and ignores table limits and finite bankrolls. It changes the pattern of wins/losses but not the negative EV of a game with a house edge.
  • Moneyline
    A sports bet on which team or player will win outright, with no point spread. In American odds, favourites have minus numbers (e.g., -150) and underdogs have plus numbers (e.g., +200).

N

  • Negative Expectation Game
    A game where the expected value is negative for the player over time (almost all casino games when played in the standard way). You can still enjoy them as entertainment, but you should expect to lose money long-term.

O

  • Odds
    The price of a bet, representing both potential payout and implied probability. Different formats (American, decimal, fractional) express the same underlying idea. See Odds Explained.
  • Over/Under (Totals)
    A sports bet on whether the combined score of both teams will be over or under a line set by the sportsbook (e.g., Over 46.5 points). The actual winner of the game doesn’t matter for this bet.

P

  • Parlay
    A bet that combines multiple selections (legs) into one. All legs must win for the parlay to pay out. Parlays offer higher potential payouts but much lower probability of winning than single bets. Our parlay calculator helps estimate payouts and implied probabilities.
  • Progressive Jackpot
    A jackpot that grows as players make wagers, with a small slice of each bet added to the prize pool. The eventual winner receives a very large payout, but the average EV for regular spins still reflects the game’s RTP and volatility.
  • Push
    A result where neither side wins or loses – for example, a tie in some blackjack situations or a point spread that lands exactly on the line. Your stake is typically returned.

R

  • Random Number Generator (RNG)
    Software that produces a stream of random outcomes used to determine results in digital casino games (slots, some table games). Properly tested RNGs ensure unpredictability within the game’s rules. See RNG Myths: Are Games Rigged?.
  • Risk of Ruin
    The probability that you’ll lose your entire bankroll before reaching your goals. Higher bet sizes, higher house edges and long sessions increase risk of ruin. Good bankroll management aims to keep this risk low.
  • Rollover / Wagering Requirement
    The amount you must bet before bonus funds (or winnings from a bonus) become withdrawable. For example, a 10x wagering requirement on a $100 bonus means you must wager $1,000 before cashing out bonus-related funds.
  • RTP (Return to Player)
    A long-term percentage indicating how much of all money wagered on a game is expected to be returned to players as winnings. For example, 96% RTP means the game keeps about 4% long-term. Remember, this is an average over huge numbers of plays, not a guarantee for your session.

S

  • Session
    A single block of gambling time, from when you start playing to when you stop and cash out or log off. Good session rules (time limit, loss limit, win goals) help you avoid tilt and excessive losses.
  • Short-Term vs Long-Term
    Short-term refers to individual sessions or small numbers of bets, where results can swing wildly away from expected averages. Long-term refers to many repeated bets, where results tend to move closer to the house edge or your EV. Understanding this difference is key to avoiding the gambler’s fallacy.
  • Single-Zero Roulette (European)
    Roulette with one zero on the wheel, giving the house a lower edge than double-zero (American) roulette. If you play roulette at all, this is usually the better choice from a math perspective.
  • Sportsbook
    A site or physical location where you place bets on sports and events. Offers moneylines, spreads, totals, props, futures and more, each with their own odds and implied probabilities.

T

  • Tilt
    An emotional state where frustration, anger or excitement leads you to abandon your usual rules and make worse decisions – chasing losses, raising stakes, or playing longer than intended. See Tilt Control & Session Rules.
  • Total (Game Total)
    In sports betting, the combined score of both teams. Over/Under bets (totals) are wagers on whether the final score will be above or below the sportsbook’s line.

U

  • Unit
    A fixed size of bet that represents a small percentage of your bankroll (for example, 1 unit = 1% of bankroll). Using units helps normalize bet size decisions and track results without obsessing over exact dollars. See our upcoming sports betting bankroll guides for examples.

V

  • Vig / Juice (Vigorish)
    The built-in commission or margin the sportsbook takes on bets, reflected in the odds they offer (e.g., -110 instead of a true 50/50 -100). It’s the sports betting version of the house edge.
  • Volatility (Variance)
    How swingy a game is in the short term. High-volatility games (many slots) can produce long dry spells and occasional big wins. Low-volatility games produce more frequent but smaller results. Our Slots, RTP & Volatility guide explains how this affects your experience.

W

  • Wager
    Any bet or stake you place on a game or event. “Wagering” also refers to the total amount of betting you do, especially when meeting bonus requirements.
  • Wagering Requirement
    See Rollover / Wagering Requirement above – the amount you must bet before bonus funds can be withdrawn. Always check game contribution percentages too, as some games count less toward wagering than others.
  • Win Rate
    The percentage of bets you win over time. In negative EV games, even a high win rate can still lose you money if your losses are larger than your wins. In sports betting, comparing your win rate to the break-even percentage at your usual odds tells you whether you’re beating the vig.

What to Read Next

If you’ve made it this far, you already care more about the math and mindset than most players – that’s a good sign. The next best steps: