Definition of illegal

Anything that causes a foul according to the rules of a game.

24 Random Essential Billiards Terms

Any shot where the cue ball is intentionally jumped into the air to clear an obstacle
A predetermined number of games, usually played for a specified sum of money. Contrast race (a predetermined number of wins). Informally, sets may refer to gambling more generally, as in "I've been playing sets all day", even when the format is actually races or single games.
This is a simple method of gambling where bets are determined between each game instead of playing matches.
The Union Mondiale de Billard (French for World Union of Billiards) is the world governing body for carom (carambole) billiard games. The organization was founded in Madrid, Spain on 1 June 1959, and is dedicated to promoting the modern carom billiards games. The UMB monitors and controls international carom competitions and tournaments, and organizes an annual World Three-cushion Billiards Championship.
To intentionally lose a game, e.g. to disguise one's actual playing ability. An extreme form of sandbagging. See also hustle. See also Match fixing for the synonym "tank", used in sports more generally.
This is the imaginary line that a ball would need to follow in order for it to result in an effective bank shot.
In snooker, the colour ball that is worth three points, being the second-least valuable colour behind the yellow. It is one of the baulk colours.
This shot refers to using heavy follow to push through an object ball on its way to its destination.
Used in snooker in reference to the position of the cue ball. It is "below" the object ball if it is off-straight on the top cushion side of the imaginary line for a straight pot (e.g. he will want to finish below the black in order to go into the reds).
Accidentally causing the cue ball or any object ball to leave the table. It is normally a foul.
Same as cheating the pocket. Principally used in snooker.
When an opponent either purposely successfully executes a defensive shot or misses their shot resulting in a bad leave for the next player.
Example: "I was left bad every time he missed his shot".
The BCA Pool League is one of the major amateur pool leagues in the United States and is present in over a dozen other countries outside the U.S., with a significant presence in Canada
A player skilled at very thin cut shots, and shots in which a ball must pass cleanly through a very narrow space (such as the cue ball between two of the opponent's object balls with barely enough room) to avoid a foul and/or to pocket a ball. Such shots may be referred to as "surgery", "surgical shots", "surgical cuts", etc. (chiefly US, colloquial). See also feather (US) or snick (UK).
Basic cue tip contact points on the cue ball to impart various forms of spin. Top spin is also known as follow, side spin as english, and bottom spin as back spin, draw or screw.Rotational motion applied to a ball, especially to the cue ball by the tip of the cue, although if the cue ball is itself rotating it will impart (opposite) spin (in a lesser amount) to a contacted object ball. Types of spin include top spin, bottom or back spin (also known as draw or screw), and left and right side spin, all with widely differing and vital effects. Collectively they are often referred to in American English as "english". See also massé.
A ball positioned near a pocket so that a particularly positioned object ball shot at that pocket will likely go in off it, even if aimed so imperfectly that if the warrior was absent, the shot would likely result in a miss. Usually arises when a ball is being banked to a pocket.
When a successful non penalized break is achieved which gives the object balls a broad spread on the table.
A fast paced offensive game similar to 9-ball but only using balls numbered 1 through 7.
Pocketing the 7-ball wins the game. Under the current pro rules of 7-ball, any missed shot gives your opponent ball-in-hand.
A bye is a missing team or player on a league schedule or tournament bracket. In other words, a person or team does not have an opponent that date (schedule) or round (tournament bracket). If a team or player has a bye on a scheduled date, they will not be playing that day. If a team or player has a bye on a tournament bracket, they automaticly advance to the next round without having to play another team or person.
To intentionally rebound the cue ball off both of the pocket points to achieve position.
This is a series of angled rails present within some pool tables that directs pocketed balls to a central location on the table for retrieval after the game.
This the area behind the pocket points before the pocket. The ball can get behind here and rest waiting to be pocketed, or the cue ball can get corner hooked in this location. Different tables feature a smaller or larger area here which can make these situations more or less achievable.
Either to hit the balls hard with no intention in mind other than to get lucky (or 'hit-and-hope'), or to shoot hard at the money ball ball with the same intention. Compare slop and fluke.
Artistic pool is a trick shot competition, inspired by the related discipline of artistic billiards.