A Guide to Slot Machine Terminology

Within gambling there are lots of different words and associated terminology for each type of game. Here we take a look at online slots and some of the terminology associated with them.

A Guide to Slot Machine Terminology

From their inception in the 19th century to the modern day, slot machines have provided a fun and exciting outlet for opportunistic gamblers throughout the world. Whether you have refined your slot machine strategy in bricks and mortar casinos or one of the many virtual outlets listed here, you will no doubt have learned a great deal both in terms of gameplay and the glossary of terms used to describe components of the experience. 

There is a particularly high ratio of specialist terms and phrases used to describe various aspects of slot machine gaming, and it is important that novice players in particular understand these and their precise meaning. With this in mind, consider the following terms and how they are applied within the game:

Bonus Feature

Almost all contemporary slot machines (both online and off) include bonus features or special stops and images that trigger instant cash pay-outs. The quantity and nature of these vary depending on specific game and the cost per spin, although many take the form of wild cards or themed symbols. These are often integral to the narrative of the game in question, while a growing number of online operators are using free spin bonus packages to entice new players to partner with them. These are usually offered as part of a welcome package and exclusively available to new players who have recently registered.

The Hold Percentage

Similar to the house edge in blackjack and roulette, slot machines have a hold percentage that varies between specific games and operators. This is a simple term that refers to how much of a player’s money the casino keeps during the course of a game, and is universally displayed as a fixed percentage. A 99% slot machine will keep a single pound while returning £99 back to the player, for example, and although this rate is extremely rare it is important to check the hold percentage associated with every game that you play. As a general rule, slot machines offer a hold percentages somewhere between 90% and 94%.


A term exclusive to slot machine gaming, the payline refers to the line at which winning reel combinations must land in order to deliver a fixed pay-out. Machines can feature multiple paylines, and this is usually determined by the cost of each spin and the amount of capital that a slot earns within throughout the course of a game. Some modern online slots feature as many as 50 paylines, for example, while there are also simpler machines that offer far less and cost barely anything to operate.