20+ years in the gambling industry including 13+ years playing and reviewing slots.
New to slot sites? Confused by the jargon? This complete A–Z glossary of slot machine terms explains everything from paylines to volatility so you can spin with confidence. Whether you're trying slot games in demo mode or going for real-money wins, understanding the terminology is the first step to better gameplay.
What is a Slot Glossary and Why It Matters?
Online slot games may look simple on the surface, but under the hood, there’s a world of features, mechanics, and game types. Learning the terminology helps you:
- Choose games that suit your budget and risk profile
- Understand what’s happening during bonus features
- Take advantage of features like free spins and wilds
This glossary is your go-to guide. Bookmark it, refer to it, and play smarter.
How to use this glossary
A-Z Slots Glossary
Confused by online slot terms? I’ve got you covered with OLBG’s complete A–Z Online Slots Glossary, Learn what RTP means, how paylines work, and what symbols to watch out for. Whether you’re new to slots or a seasoned spinner, it’s a must-read.
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3-Reel Slot: An online slot game with 3 reels which are commonly found in land-based casinos (i.e. Pragmatic Play’s Big Bass Bonanza 3 Reeler).
5-Reel Slot: These slot games come with 5 reels as standard and are the most common type found online (i.e. Light & Wonder’s Rainbow Riches).
243 Ways to Win: A slot game with 243 ways to win that is played across 5 reels with winning combinations awarded when you land 3 or more matching symbols from left to right in any position. (3 x 3 x 3 x 3 x 3 = 243). The most popular 243 ways to win slot is Microgaming/Stormcraft Studios’ Immortal Romance.
1,024 Ways to Win: A slot game with 5 reels, 4 rows and 1,024 ways to win. Like 243 ways to win games, there is an extra row for more ways to win (4 x 4 x 4 x 4 x 4 = 1,024). A 1,024 ways to win slot is 4ThePlayer’s 4 Pirate Chests.
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Auto Play: Also known as autoplay, this allows the user to set a certain number of automatic spins (i.e. 100). Auto Play is prohibited in the UK due to the Gambling Commission’s regulations.
Active Payline: This determines how many paylines are active during a single spin. With some slot games, you can play with all paylines or as many as you choose (i.e. this is possible in Novomatic’s Book of Ra Deluxe where you can play with between 1 and 10 paylines active).
Avalanche: When a winning combination is formed, the Avalanche feature is activated. Winning symbols then disappear with new ones fall down into the empty positions. Allowing for successive wins, the first Avalanche slot was NetEnt’s Gonzo’s Quest.
All Ways: All Ways slots come with paylines or ways to win that pay no matter the direction. It’s often referred to as Scatter Pays with Relax Gaming’s Money Train 4 a popular choice.
Ante Bet: Found in many slot games, the Ante Bet feature typically increases your chances of landing scatter or bonus symbols to trigger the all-important Free Spins feature. Ante Bet can be found in most Pragmatic Play slots.
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Balance: This is the amount of credit/money you have in your slot or casino site account. To add funds to your account, check out the range of casino payment methods available.
Base Game: This is the standard game played when you fire up a slot game. From here, you can trigger various bonus features (more details below).
Bet: Also referred to as the stake, this is the amount you’ll play for when you spin the reels. The minimum bet is typically between 10p and 20p a spin with the maximum up to £5 per spin in the UK (or up to £2 if between 18-24).
Bonus Feature: A Bonus feature is an interactive mini-game triggered by scatters or bonus symbols. Most slot games come with bonus features including free spins or multipliers. With slot providers throwing in various combinations, check my guide to the best slots with bonus features for more details.
Bonus Buy: Prohibited in the UK, the Bonus Buy feature lets your purchase direct access to a bonus feature. For example, all Nolimit City slots come with several options with added extras.
Book of: Popularised by Book of Ra Deluxe in 2005, ‘Book of’ slots come with a Free Spins feature of sorts where a symbol is chosen to act as the expanding symbol. When it appears on the reels, it expands to take over the entire reel. The higher the value of the symbol and the more of them that appear, the bigger the win potential. Check out my guide to the best ‘Book of’ slots.
Branded Slot: A branded slot game is a game based on a movie/film, television show/series, rock band or musician, game show or even video game. Examples include Big Time Gaming’s Monopoly Megaways and Blueprint Gaming’s The Goonies.
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Cascades: Similar to the Avalanche feature, a winning combination sees the winning symbols removed from the reels with new symbols replacing them. Leading to cascading wins, the process repeats itself until no more new wins are formed. An example is Relax Gaming’s Plunderland.
Classic Slots: This refers to the most traditional and simple slot games typically with 3 reels. Originating from land-based casinos, they typically have a fruit theme with little or no bonus features.
Coins: Found in older slot games, your balance is shown in coins rather then a monetary value. For a 10 payline game, you’ll normally play with 10 coins per spin.
Coin Value: This is the value of each coin. Affecting your stake bet/stake per spin, an example is Play ‘n GO’s Book of Dead where you can set the number of paylines, coins and coin value on each spin.
Cluster Pays: Slots with Cluster Pays are games that don’t use traditional reels or paylines. Taking place on a grid, a cluster of matching symbols will award a winning combination. Typically need 5 or more matching symbols connected vertically and/or horizontally, the bigger the cluster, the bigger the payout. With Push Gaming’s Jammin’ Jars the best example, see my Cluster Pays slots guide for more details.
Collect: Found in older slot games, you can ‘collect’ your win which transfers the amount to your balance.
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Demo Slots: Demo or free slot games are fun versions of the real money equivalent. This means you can try a game with no risk or real-money commitment.
Drops & Wins: These are gamed from Pragmatic Play that are part of their Drops & Wins promotion. By playing their games, you can win daily prizes in slot tournaments and random prize drops with a total of £2 million in cash every month. The promotion runs every 3 months typically.
Dream Drop: These are games (primarily from Relax Gaming) that give you the chance of win 5 Dream Drop progressive jackpots. The Mega Jackpot pays up to €3 million and is won every 1.5 months on average. Check out the best Dream Drop jackpot slots for your chance to win.
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Enhancers: Found in Nolimit City games, Enhancers trigger certain bonus features or modifiers when filled with the relevant symbol.
Expanding Wilds: Often seen during a Free Spins feature, these are wild symbols that ‘expand’ to cover/take over a whole reel. NetEnt’s Starburst XXXtreme offers them.
Extra Spins: Found in a Free Spins feature, extra spins are additional free spins you can win by typically land 3+ Scatter/Bonus symbols.
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Feature Buy: Described above as Bonus Buy, it lets you purchase your way into a bonus feature for a fee.
Fixed Jackpot: This is a pre-determined jackpot amount you can win in a slot game. In IGT’s Lucky Larry’s Lobstermania 2, you make picks in the Buoy Bonus feature for fixed cash prizes.
Free Spins: Also referred to as a Free Spins feature, they can be triggered in-game or claimed via promotions. Check OLBG’s free spins page for current offers. I also recommend you check my list of no wagering free spins offers which come with no strings attached (i.e. what you win is yours to keep).
Best Free Spins No Wagering Offers 2025
Fruit Machine: A fruit machine is a classic slot game found in pubs and arcades. Although simple, the name derives from the fruit symbols on the reels.
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Gamble Feature: Found in many games, you can try to double winnings in a side game, e.g., red or black card pick.
Gamble Responsibly: This is information for players on how to stay safe when playing slots online. All sites offer guides and tools (such as Time-Outs) so you can manage your gambling activity responsibly.
GigaBlox: This is a mechanic created by Yggdrasil Gaming which sees super-sized symbols on the reels. Due to its popularity, Yggdrasil has licensed the mechanic to various providers including 4ThePlayer and Peter & Sons.
Giant Symbols: Similar to GigaBlox, these are also referred to as colossal symbols and are mega-sized symbols that increase your chances of winning. They feature in several Slotmill slots including Emberfall and Ragnarok 40k.
Grid Slot: Games like Play ‘n GO’s Reactoonz use a grid instead of reels and paylines and use either Cluster Pays or Scatter Pays wins.
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High Volatility: Slots which are high variance offer bigger but less frequent wins. To are riskier but with higher reward potential to compensate: NetEnt’s Dead or Alive 2 is a prime example.
Hit Frequency Rate: This is the average number a winning combination occurs in a slot game. In Pragmatic Play’s Big Bass Bonanza for example, the 13% hit frequency rate meaning a win will land every 7.69 spins on average.
Hold & Spin: When you land a winning combination lands, the winning symbols are held in position with the other positions respinning. If you add to the win, the process continues until no more wins are possible. A final payout is then awarded. Playtech’s Blue Wizard is a good example.
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Instant Win: Offering an immediate payout, a random prize or fixed reward is triggered by bonus features.
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Jackpot: There are different types of jackpots including fixed jackpots or progressive jackpots. Offering a reward which is either pre-determined or increasing in value, a jackpot is also a term used to describe a slot game’s max win total.
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Kicker Symbol: Found in slot machines, a kicker is another word for a wild or scatter symbol that helps complete a winning combination or trigger a bonus feature.
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Lines: Another term for paylines, this determines how winning combinations are created or formed.
Low Volatility: Low variance slot games often frequent but smaller wins which are ideal for longer sessions and smaller budgets. The most popular low volatility game is NetEnt’s Starburst.
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Max Bet: This is the highest amount you can bet or stake per spin. In the UK, the maximum bet is £5 or £2 if under 25. In some jackpot slots, like Playtech’s Jackpot Giant, the max bet is required to have a chance of winning the progressive jackpot.
Max Win: This is the term used to describe the maximum a slot game can pay out. Also known as a game’s jackpot, the highest max win slot is Nolimit City’s Tombstone Slaughter which offers 500,000 x bet max wins.
Max Win Probability: This is a term to describe your chances of winning the max win. Included in reviews (where available), your chances increase when triggering certain bonus features compared to the base game.
Mechanic: This is the engine a slot game runs on. For example, they may be a reels and payline slot game whilst others use Megaways, Cluster Pays and Scatter Pays.
Megaways: Pioneered by Big Time Gaming, Megaways slots don’t have a pre-determined number of ways to win. On each spin, the number of symbols appearing on each reel is random normally awarding up to 117,649 ways to win. For more details, check out my Megaways slots guide which highlights the 10 best games, how the mechanic work and much more.
Best Megaways Slots Guide 2025
Mobile-Friendly: This is the term used to describe slot games that can be played on smartphone and tablet devices. Using HTML5 technology, the game detects your device and serves the appropriate version to make better use of the full screen. All slots these days are ‘mobile-friendly’.
Modifier: Another term for a bonus feature, a modifier will enhance winning potential by adding multipliers, wilds and various extras and features to the play.
Multiplier: A multiplier is a feature that multiplies your winnings by a specific factor (i.e. 2x or 5x). Multipliers can be found in special symbols (such as wilds) or apply to every spin in the Free Spins feature.
Mystery Symbol: These symbols (when a certain number land simultaneously during a spin) will transform into a randomly chosen symbol for a higher chance of a winning combination. Mystery symbols are common in Megaways games.
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Nudge: This feature/modifier moves a reel or symbol 1 position left or right to help create a winning combination. Mostly found in retro or classic slots, an example is Hacksaw Gaming’s Danny Dollar.
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Overlay Symbol: An overlay symbol will land on top of regular symbols which trigger bonus features or modifiers. You’ll come across overlay wilds which are found in Nolimit City’s Whacked.
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Paylines: A payline determines the specific line-up of symbols to award a winning combination. Most slot games have 10 to 20 paylines with Megaways slots typically offering up to 117,649.
Payout: This is a term to describe the win amount from a certain spin or bonus feature. For example, a 3 of a kind win with Diamond symbols in Bonanza Megaways will award a 5 x bet payout.
Paytable: Available in every slot game, it displays symbol payouts and information of all bonus features. It’s like a blueprint to how a slot game pays and what extras you can trigger/play.
Penny Slots: Also referred to as low stake slot machines, these are games that allow you to play from 1p (per payline) a spin. So if a slot game has 10 paylines, the minimum bet will be 10p. Check out the best penny slots in the UK.
Pick and Win: This term refers to slot games where you make a pick in the bonus feature to win prizes including cash rewards, free spins or modifiers. In Big Bass Xmas Xtreme, you pick to win free spins, guaranteed fish, Fisherman Wilds or symbol removals.
Progressive Jackpot: A type of slot game, jackpot slots as they are commonly known come with progressive jackpots which are pooled across multiple casino and slot sites. The more players play, the bigger the progressive jackpot(s) grow. Check out my guide to the biggest and best progressive jackpots slots with Microgaming’s Mega Moolah the most popular: you’ll discover real-time jackpot trackers too!
Biggest Jackpot Slot Games
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Quick Spin: This optional setting speeds up gameplay with faster reel animations. Not allowed in the UK, the minimum time a spin will take for UK players is 2.5 seconds.
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Reels: The vertical columns in a slot game, most slots usually have 5 reels with classic fruit machines containing 3.
Respins: A bonus feature, respins are triggered by certain symbols or when you nearly land a winning combination,. Awarding a respin allows for an extra spin to trigger a bonus feature or land a winning combination. NetEnt’s Starburst is the best example where you get up to 3 respins with expanding Starburst Wilds.
RTP: Short for Return to Player (rate), it’s the term that describes the payback percentage of a particular slot game. With the average around 96%, you’ll win £96 back when you stake £100 on average. Compare the highest RTP slots in my guide which range up to 99.07%.
Highest RTP Slots & Best Payout Slot Machines
Random Number Generator: All slot games use a Random Number Generator (RNG for short) which decides the result of each spin. Completely random, it ensures fairness on each spin.
Royal Symbol: Found in most games, royal symbol is a term used to describe symbols found in playing cards. The most common are A, K, Q, J and 10.
Retrigger: A retrigger is a term used to describe when you win additional free spins during a bonus feature by land a certain number of scatter/bonus symbols. Some slots offer the chance for unlimited retriggers for infinite free spins.
Reaction: This is another term used to describe a cascade, avalanche or tumble which sees winning symbols disappear from the reels to be replaced by new ones.
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Scatters: Also known as a Bonus symbol, scatter symbols usually trigger or active bonus features (i.e. 3 Scatters will activate the Free Spins feature).
Slot Provider: These are the companies that create slot games. All licensed by the UKGC, check out the best slot game providers such as Nolimit City, Hacksaw Gaming, Pragmatic Play and Play ‘n GO.
Best Slot Game Providers: with Dedicated Guides
Slot Tournament: These are competitions set out by slot or casino sites on specific slot games which give you the chance to win cash prizes or free spins. Check out best sites for slot tournaments for more details.
Spin: This is the action a player must take to play a slot game. Spin buttons vary from provider to provider though but tend to be the most prominent on the screen.
Stacked Symbols: These are symbols are appear multiple times in a reel and a great for filling reels to form winning combinations. Light & Wonder’s Zeus offers them.
Sticky Wilds: These wild symbols that remain in play for several spins or during a bonus feature (i.e. free spins). In Pragmatic Play’s The Dog House Megaways, there are up to 7 sticky wilds on every reel which come with multipliers up to 3x.
Symbols: These are the images that appear on the reels. You need to land a certain number of matching symbols to form a winning combination (across a payline or Cluster/Scatter formation).
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Themed Slot: These are slot games with a particular theme (i.e. ancient Egyptian themed slots). My slot themes page highlights the most popular slot game themes with the best games for each.
Slot Themes: List of the Most Popular Themes & Slot Games
Tumble: When a winning combination or outcome lands, winning symbols are removed and replaced by new symbols tumbling in. Tumble is an alternative term for cascade, avalanche or reaction. There is a Tumble feature in Pragmatic Play’s Gates of Olympus slot.
Turbo Mode: Similar to Quick Spin: this feature offers ultra-fast gameplay and skips animations for faster sessions. It’s also prohibited in the UK.
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Unlimited Multiplier: This describes a multiplier that can increase with each win, with no limits of course. It’s commonly found in Megaways slots.
UKGC: Short for the UK Gambling Commission, this is the governing body in the UK that oversees all gambling activity and issues licenses to slot sites and slot providers operating in the UK. Find out more by visiting the Gambling Commission’s official website.
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Variance: This is another term for volatility which is described directly below.
Volatility: This term defines how a slot game pays out over time: specifically how often and how much you’re likely to win. There are various types ranging from low volatility to insane volatility. Check out my guide to slot volatility for more details.
Slot Volatility Explained: How Risk Levels Impact Your Slot Play
Video Slot: This is the term commonly used to describe a modern slot game. Video slots use animated reels than static ones for an enhanced visual experience.
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Wager: An alternative term for ‘bet’, it determines the amount you play per spin.
Wagering Requirements: Also known as play through requirements, these dictate how many times you need to stake or wager your bonus/free spins before you can cash out winnings or the bonus amount. This applies to a slot site’s welcome offer.
Wilds: Wild symbols act as jokers and substitute/replace other symbols to complete winning combinations. There are so many types of wilds these days including multiplier wilds, expanding wilds, sticky wilds, spreading wilds, walking wilds, stacked wilds and several combinations of all!
Win Both Ways: These are slots with win both ways functionality: i.e. from left to right and right to left. NetEnt’s Starburst is the best example.
Winning Combination: This term describes to way to land a win in a slot game. Some require matching symbols across a payline or a number of symbols appearing a cluster (i.e. connected vertically and/or horizontally).
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xWays: This is a mechanic found in Nolimit City games which sees more symbols added to the reels to dramatically boost win potential. Nolimit City has plenty of unique, in-house xMechanics including xInfectious Ways, xSplit, xNudge, xBomb and xBizarre.
Final Thoughts
Learning how to read a slot machine glossary is more than trivia: it’s about giving yourself the best chance to play smart. Whether you’re trying demo slots or chasing progressive jackpots, knowing the basics lets you enjoy every spin more.
As more and more slot games are released, new concepts, bonus features and mechanics are created meaning this guide will continue to grow. If you’re like more terms added, please feel free to reach out and contact me.
