A complete A-Z reference of online slot terminology — from Autoplay to Ways to Win — explaining exactly what each term means, how it affects the way a slot plays, and linking through to this site's fuller guides wherever a term deserves deeper coverage

Slot terminology gets thrown around constantly across reviews, paytables, and game information screens, but rarely explained in one place. This glossary defines every major term in plain language, and points to a fuller guide on this site wherever a term is covered in more depth elsewhere.

A

Autoplay — A setting letting a series of spins run automatically at a fixed stake without requiring a manual spin each time. UK-licensed slots are subject to minimum spin-speed and autoplay restrictions under Gambling Commission rules, referenced throughout this site's provider hub guides.

Avalanche — NetEnt's own branded term for the cascading wins mechanic, covered in full in this site's NetEnt Provider Hub guide. See also Cascading Wins below.

Achievements Engine — Quickspin's proprietary loyalty mechanic rewarding in-game milestones with Loyalty Tokens, covered in this site's Quickspin Provider Hub guide.

B

Bonus Buy / Feature Drop — A mechanic letting a player pay a fixed cost to directly purchase entry into a bonus round rather than triggering it through ordinary play. Not available on UK-licensed sites — stripped from UK builds entirely under Gambling Commission requirements (RTS requirement 14A), covered in detail in this site's Slot Bonus Features Explained guide and referenced across the NoLimit City and Push Gaming provider hub guides specifically.

Bonus Round — A distinct feature, separate from ordinary base-game spins, usually offering enhanced win potential — free spins, an expanding-symbol sequence, a pick-and-click bonus, or a dedicated mini-game.

C

Cascading Wins — Also called Avalanche or Tumble depending on the studio. Winning symbols clear from the reels and new symbols drop into place, potentially creating further wins from a single spin. Covered in this site's Slot Bonus Features Explained guide.

Cluster Pays — A win structure based on matching symbols forming a connected cluster (horizontally or vertically adjacent) rather than falling along a fixed payline. Used by titles like Reactoonz, covered in this site's Red Tiger Provider Hub guide.

Collector / Meter Feature — A mechanic where specific symbols accumulate on a visible meter across spins, paying out or triggering a bonus once filled. ELK Studios' CollectR system, covered in this site's ELK Studios Provider Hub guide, is a notable branded example.

D

Dead Spin — A spin producing no win at all. Genuinely common on higher-volatility titles, where win potential concentrates in rarer, larger bonus-round outcomes rather than frequent smaller base-game wins.

Dynamic Reels — Reels that change height or symbol count from spin to spin, the underlying structure behind Megaways and similar variable-reel mechanics, covered in this site's Megaways Slots Explained and Big Time Gaming Provider Hub guides.

E

Each-Way — Not a slots term specifically, but worth flagging since it appears in casino and sports contexts alike; see this site's Golf Betting Explained guide for the sports-betting version of each-way terms.

Expanding Symbol — A symbol that grows to fill an entire reel once landed, most famously the mechanic behind the "Book of" slot format, covered in full in this site's Best "Book of" Slots guide.

Extreme Volatility — A volatility classification beyond standard "high," describing titles with win potential concentrated in especially rare, especially large outcomes. Relax Gaming's Money Train series, covered in this site's Relax Gaming Provider Hub guide, is a commonly cited example.

F

Feature Drop — See Bonus Buy above; Push Gaming's own branded term for the mechanic, covered in that studio's provider hub guide.

Free Spins — A bonus round awarding a set number of spins played without further staking, commonly triggered by landing a set number of scatter symbols, often with an added feature (multipliers, sticky wilds, or an expanded reel set) active during the round.

G

Gamble Feature — A double-or-nothing mechanic offered after a winning spin, commonly a card-guessing game (colour or suit), letting a player risk a win for a chance at doubling or quadrupling it. Common on Novomatic's classic catalogue, covered in this site's Novomatic Provider Hub guide.

GO Collect — Play'n GO's proprietary collection-meter mechanic layered onto established titles like Book of Dead, covered in this site's Play'n GO Provider Hub guide.

H

Hit Frequency — How often a spin produces any win at all, expressed as a percentage or a ratio. A separate figure from RTP and volatility — a title can have a high hit frequency of small wins, or a low hit frequency concentrated in larger ones.

High Volatility — A classification describing titles where wins are less frequent but larger on average when they occur, as against low or medium volatility titles offering more frequent, smaller returns.

I

In-House Development — Games built entirely by a studio's own team rather than licensed or acquired from a third party. Thunderkick, covered in this site's Thunderkick Provider Hub guide, specifically describes its catalogue as 100% in-house.

Instant Prize — A mechanic integrating cash-reward symbols directly into the reel grid, paying out immediately when landed. Credited to Push Gaming as an early industry example, covered in that studio's provider hub guide.

J

Jackpot, Must-Hit-By (Mystery Jackpot) — A jackpot guaranteed to trigger within a fixed window or threshold, distinct from an open-ended progressive. Red Tiger's Daily Drop Jackpots network, covered in this site's Red Tiger Provider Hub guide, is a notable example.

Jackpot, Progressive — A jackpot that grows continuously as players contribute a small percentage of every stake, with no guaranteed trigger point. Covered in full in this site's Progressive Jackpot Slots guide.

L

Low Volatility — A classification describing titles offering frequent but smaller wins, as against the larger, less frequent returns typical of high or extreme volatility titles.

Loyalty Tokens — Rewards earned through Quickspin's Achievements Engine (see above), redeemable at a fixed 1:1 ratio with currency.

M

Max Win — The largest possible payout a single spin can produce, expressed as a multiple of the triggering stake (for example, 20,000x). A separate figure from RTP, and not a guarantee any individual spin will approach that ceiling.

Megaclusters — Big Time Gaming's proprietary mechanic combining an expanding grid with cluster pays, covered in this site's Big Time Gaming Provider Hub guide.

Megapays — Big Time Gaming's shared, multi-title progressive jackpot mechanic, covered in this site's Big Time Gaming Provider Hub guide.

Megaways — Big Time Gaming's licensed variable-reel mechanic generating up to 117,649 ways to win, covered in full in this site's Megaways Slots Explained and Big Time Gaming Provider Hub guides.

Multiplier — A value that increases a win by a set factor (2x, 5x, 10x, and so on), applied either to individual symbols, whole spins, or accumulating across a bonus round's duration.

Must-Hit-By Jackpot — See Jackpot, Must-Hit-By above.

N

Ni — Not a slots term; included here only to note there is no standard slots term beginning with N beyond nudge features (see below).

Nudge Feature — A mechanic letting a reel "nudge" up or down by one position after the initial spin result, potentially completing a winning combination. A classic mechanic inherited from land-based arcade-machine slot design, similar in heritage to the gamble feature covered above.

O

Operator Configuration — Many providers supply a slot's RTP as a range of pre-approved values (for example, 92.00%–96.50%), with the specific figure a player receives determined by which configuration a given operator has chosen to run. This is why the same title can show a slightly different RTP at two different UK-licensed casinos — always worth checking a specific game's own information screen rather than assuming a headline figure applies everywhere it's listed.

P

Paylines — Fixed lines across the reels along which matching symbols must land to form a win, the traditional structure that Megaways and other variable-reel or ways-to-win systems were built to move beyond.

Progressive Jackpot — See Jackpot, Progressive above.

Q

Quantum Leap — Reactoonz's own branded bonus feature, adding an extra wild-generating mechanic to the title's cluster-pays base game, covered in this site's Red Tiger Provider Hub guide.

R

Re-Spin — A single additional spin awarded after a specific outcome, often with part of the reel set locked in place — the mechanic behind Hold & Win-style features.

RNG (Random Number Generator) — The certified system determining a spin's outcome, ensuring results are independent and unpredictable from one spin to the next, regardless of previous results or session length.

RTP (Return to Player) — The theoretical long-run percentage of all staked money a slot returns to players over a very large number of spins, expressed as a percentage (for example, 96.5%). A long-run statistical average, not a guarantee for any individual session — covered in context throughout this site's provider hub guides.

S

Scatter Symbol — A symbol that triggers a bonus feature (commonly free spins) when a set number land anywhere on the reels, regardless of payline position.

Sticky Wild — A wild symbol that remains in place across multiple spins or re-spins rather than resetting after a single spin.

SuperSpinners — Print Studios' proprietary mechanic multiplying adjacent multiplier values against one another for exponential win potential, covered in this site's Print Studios Provider Hub guide.

T

Top Slot — A separate two-reel display used in live game shows like Crazy Time, locking in a targeted segment and multiplier value before the main wheel spins. Covered in this site's dedicated Crazy Time Explained guide.

Tumble — Pragmatic Play's own branded term for the cascading wins mechanic. See Cascading Wins above.

U

UKGC (UK Gambling Commission) — The statutory regulator overseeing all gambling activity offered to UK players, including online slots. Every operator legally accepting UK players must hold a UKGC operating licence, which in turn imposes the RTP disclosure, stake-limit, bonus-buy restriction, and spin-speed/autoplay requirements referenced throughout this site's provider hub and game guides. Referred to as "UK-licensed" throughout this site as shorthand for a site holding this licence.

V

Volatility — How a slot's win potential is distributed — low volatility spreads smaller wins more frequently, while high or extreme volatility concentrates win potential into rarer, larger outcomes. A separate concept from RTP, referenced throughout this site's provider hub guides.

W

Ways to Win — A win structure counting matching symbols across adjacent reels regardless of exact position, rather than requiring symbols to land along a fixed payline. Megaways (see above) is a variable-reel extension of this same underlying principle.

Wild Symbol — A symbol that substitutes for other standard symbols to help complete a winning combination, with variants including expanding wilds (growing to fill a reel), sticky wilds (persisting across spins), walking wilds (moving position each spin), and multiplying wilds (adding a multiplier to any win they help form).

X, Y, Z

xNudge / xSplit — NoLimit City's own proprietary mechanics extending the classic nudge feature and adding a symbol-splitting system respectively, covered in this site's NoLimit City Provider Hub guide.

X-iter — ELK Studios' proprietary mode-selection feature, letting a player choose between different risk/reward configurations before spinning, covered in this site's ELK Studios Provider Hub guide.

A Practical Note on Using This Glossary

Many of these terms describe a slot's underlying mechanic rather than its visual theme — worth reading alongside this site's Slot Themes Explained guide, which makes the case in more depth for why theme and mechanic are genuinely separate questions when choosing what to play. Studio-specific branded terms (Avalanche, Tumble, xNudge, Quantum Leap, and the many others listed above) frequently describe the same or a closely related underlying concept under a different name — checking which general category a specific branded term falls into is often more useful than treating every studio's own terminology as entirely unique.

Frequently Asked Questions

What's the difference between RTP and volatility?

RTP is the theoretical long-run percentage of staked money returned to players over a very large number of spins. Volatility describes how that return is distributed — frequent smaller wins (low volatility) versus rarer, larger wins (high or extreme volatility). A title can have identical RTP to another while playing very differently due to volatility.

What's the difference between a payline and ways to win?

A payline requires matching symbols to land along a specific fixed line across the reels. A ways-to-win structure counts matching symbols across adjacent reels regardless of their exact vertical position, generally producing more possible winning combinations per spin.

Why do so many studios use different names for the same mechanic?

Branded terminology (Avalanche, Tumble, xNudge, and others) is often a marketing and trademark choice layered onto a mechanic that's conceptually similar or identical across studios — cascading wins, for instance, functions the same way under several different studio-specific names.

Is bonus buy available on UK-licensed slots?

No — bonus buy (also called Feature Drop by some studios) is stripped from UK-licensed builds entirely under Gambling Commission requirements, covered in detail in this site's Slot Bonus Features Explained guide.

What does "hit frequency" mean?

How often a spin produces any win at all, regardless of size — a separate figure from both RTP (the long-run percentage returned) and volatility (how win size is distributed).

Does a higher max win always mean a better slot?

Not necessarily — max win is a separate figure from RTP and volatility, describing only the largest possible single-spin payout. A title with a very high max win can still have lower overall RTP than a title with a more modest ceiling.

This guide is for informational purposes and reflects general online slot terminology as commonly used across the industry — specific studios and titles may use branded variants of these terms. Always check a specific game's information screen for its own precise terminology and figures. 18+ only. UKGC-licensed operators only. Gambling problem? BeGambleAware.org | National Gambling Helpline 0808 8020 133. Information correct as of October 2026.