Definition of cluster

Two or more object balls that are touching or are close together.

24 Random Essential Billiards Terms

The way in which a player holds the butt end of the cue stick.
The wrap of the cuestick where the hand is placed, also known as the "grip area."
This is the final object ball you need to pocket in order to win a game of one pocket.
The 5 out (meaning the player getting the handicap can win by making the 5, 6, 7, 8 or 9 balls).
A bridge formed by the hand where no finger loops over the shaft of the cue. Typically, the cue stick is channeled by a "v"-shaped groove formed by the thumb and the base of the index finger.
Any shot that intentionally accounts for the elasticity of the cushions to allow a ball to bank past an otherwise blocking ball. The moving ball will sink in to the cushion very near the blocking ball giving it sufficient space to get past it or kiss off the back side of it.
Also lows, low, low ones. In eight-ball, to be shooting the solid suit (group) of balls (1 through 7); "you're low, remember", "you're low balls" or "I've got the lows." Compare solids, reds, little, spots, dots, unders; contrast high.
Chiefly Australian: Same as a force follow shot.
This is a play where the shot of the cue ball is meant to end up in a certain place to loose your turn, but makes the next attempt difficult for your opponent. The shot is turned over, but will often times lead to a foul, giving you the ball back with a different view or ball in hand. This "safety" play is important if your shot isn't ideal, and you are likely to turn the ball over anyway.
Same as cheating the pocket. Principally used in snooker.
This is the state after which the person returning the break has had the opportunity to catch and even the field after the breakers advantage.
This is when it is necessary to change a set handicap after play indicates it favors one player more than the other.
A defensive action taken when a player either has no "makeable" or "high percentage" shot or chooses to leave his opponent in a difficult situation. It is a legal shot and is not considered to be dirty pool. A safety must still conform with the rule concerning hitting the correct ball first and striking a rail afterwards. If a correct ball is accidentally pocketed while playing safe, the shooter must continue to shoot.
An agreement between two players in a tournament, one of whom will advance to a guaranteed money prize if the match is won, to give a certain percentage of that money to the loser of the match. Also known as a saver.
Ten Ball is a rotation is a rotation game very similar to nine-ball, using ten balls instead of nine, and with the 10 ball instead of the 9 as the "money ball".
The object of the game is pocket the 10-ball on any legal shot.
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.
Also pro side of the pocket and missing on the professional (or pro) side of the pocket. Sometimes "of the pocket" is left off the phrase. To err on the side of overcutting a difficult corner pocket cut shot rather than undercutting in nine ball; "missing on the professional side of the pocket." So called because experienced players understand that on a thin cut, overcutting the object ball to a corner pocket will far more often leave the object ball in an unfavorable position for the incoming opponent than will an undercut, which often leaves the object ball sitting in front of or nearby the pocket it had been intended for on a miss. By contrast, in eight-ball, except when both players are shooting at the 8 ball, the incoming player after a miss is shooting for different object balls, so this maxim does not apply, and the opposite may be good strategy as, if the object ball stays near the pocket through an undercut, it is advantageously positioned for a subsequent turn and may block the opponent's use of the pocket.
Same as duck. Derives from an easily shot ball "hanging" in the pocket.
This is another name for One Pocket pool.
This is a style of play where the player is required to stay on top of all the scoring practices. Scratches and points will disappear if they are not remembered.
As in many other sports, "legal" means not causing or likely to cause a foul (the opposite being illegal). A legal hit is one in which the requirements for a non-foul hit are met (e.g., in nine-ball, the lowest-numbered ball on the table was hit by the cue ball first, and at least one object ball was pocketed, or any ball reached a cushion, after the hit on the first object ball.). A legal shot is one in which no foul of any kind was involved (e.g. there was not a double hit by the cue, the player's bridge hand did not move a ball, etc.). A legal stroke is one in which the cue stroke obeyed the rules (e.g. the shooter did not perform an illegal jump shot by scooping under the cue ball with the cue tip). A legal ball is a ball-on, an object ball at which it is permissible for the player to shoot. And so on. The term can be used in many ways consistent with these examples ("legal pocket" in one-pocket, "legal equipment" under tournament specifications, etc.).
This is a shot where the cue ball follows directly behind the sunk object ball into the pocket right after it falls.
This is English that turns into reverse English after contact with the object ball. This will close up the angle on a bank.
White talcum powder placed on a player's bridge hand to reduce moisture so that a cue's shaft can slide more easily. It is not provided in many establishments as many recreational players will use far more than is necessary and transfer it all over the table's surface. Venues that do provide it usually do so in the form of compress cones about 6-inches tall. Some serious players bring their own, in a bottle or a porous bag that can be patted on the bridge hand. Many players prefer a pool glove. Talc is frequently mistakenly referred to as "hand chalk", despite not being made of chalk.
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.