Definition of Left

This describes balls that are not able to be made in a pocket, either because they are high up on the table, in a different pocket, or in a cluster that makes the shot difficult. This condition of being out of play obviously exists on different difficulty levels.

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".

In one pocket pool this means that you change your play based on where the count is during the game. If you are ahead you might choose more conservative shots, and if you are behind you could choose more aggressive shots.

When a ball is given as a handicap it often must be called (generally tacit). A wild handicap means the ball can be made in any manner specifically without being called.

The placement of player(s) automatically in a tournament where some have to qualify, or automatic placement in later rounds.

Same as stripes, in New Zealand. Compare yellows, high, big ones; contrast unders.

Also double-century break. In English billiards, a break of 200-299 points (i.e. double a century). Larger multi-centuries are regularly achieved. Rare in amateur play, triple centuries are routine, and quadruples not uncommon at World Professional Billiards Championships; 2007 winner Mike Russell shot four triples in the final round alone, while of sixteen competitors, three shot quadruple centuries (one once, one twice, and Russell three times). Quintuple centuries are rare even at the professional level, with only the 494 shot by nine-time World Champion Russell (who has more such titles than any other player in history as of 2007) coming close in that event. World Champion Geet Sethi holds the world record, at a duodectuple century (and then some) of 1276 consecutive points."

A pool room employee who plays with a good degree of skill.

This is when a ball is spotted because of a foul or a handicap.

A player's turn at the table, also known as an inning.

This is an imaginary player that you can attempt to run a rack against when playing a practice or training game.

This is to watch a match with such intensity that there is worry, usually because of a wager on the game.

Sometimes called a snake shot. A carom billiards shot, common in three-cushion billiards, where the cue ball is shot with reverse english at a relatively shallow angle down the rail, and spins backwards off the adjacent rail back into the first rail.

Chiefly British: Same as duck, and stemming from the same obvious etymology.

Chiefly American: The short rail at the head of the table. Traditionally this is the rail on which the table manufacturer's logo appears. Compare bottom rail, baulk rail; contrast foot rail.

A ball that is easily made from many positions on the table but which is left untouched while the rack is played, so that in the event the player gets out of position, the shooter has an insurance shot. Typically an insurance ball will be in or near the jaws of a pocket.

Describes the propensity of pockets to more easily accept an imperfectly aimed ball shot at a relatively soft speed, that might not fall if shot with more velocity ("that ball normally wouldn't fall but he hit it at pocket speed"). The less sensitive to shot-speed that a pocket is, the "faster" it is said to be.
Describes the velocity of an object ball shot with just enough speed to reach the intended pocket and drop. "Shoot this with pocket speed only, so you don't send the cue ball too far up-table."

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 ball that is left in a position that allows an easy shot, while time is spent working with other balls to better your position in the game.

Chiefly British: Short for side spin. In Canadian usage, the term is sometimes used as a verb, "to side".

Successive games won without the opponent getting to the table; a five-pack would be a package of five games.

Also swan rest. A type of rest, similar to a spider in that the head is raised by longer supporting legs, but instead of a selection of grooves on the top for the cue to rest in there is only one, on the end of an overhanging neck, so that a player can get to the cue ball more easily if the path is blocked by two or more obstructing balls. Also known as the goose neck.

This is a player that will regularly loose money to a particular player that is obviously a better player.

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.