Definition of Umpire

1- Shortened phrase of "ball-in-hand".

2 - In snooker, the ability to place the cue ball anywhere inside the boundaries of the D. This occurs at the start of a frame, and after the cue ball has been potted or forced off the table.
Also a short form of "Ball In Hand".

The overall competition between two players, two pairs of players or two teams of players, usually consisting of a predetermined number of frames or games (sometimes organized into rounds).

A three cushion billiards shot in which the cue ball first strikes two cushions before hitting the first object ball then hits a third cushion before hitting the second object ball. So called because the shot opens up like an umbrella after hitting the third rail. Umbrella shots may be classified as inside or outside depending on which side of the first object ball the cue ball contacts.

The area on the table behind the head string.
The origin of the term has been the subject of some speculation but the best explanation known is that in the 1800s, many homes did not have room for both a billiard table and a dining room table. The solution was a billiards table that had a cover converting it into a dining table. Kept in the dining room, play on such a table was often restricted by the size of the room, so it would be placed so that the head rail would face the connected kitchen door, thus affording a player room for the backswing without hitting a wall. A player was therefore either half or sometimes fully (literally) "in the kitchen" when breaking the balls.

A form of doubles play in which the two team members take turns, playing alternating shots during an inning (i.e. each team's inning consists of two players' alternating visits, each of one shot only, until that team's inning ends, and the next team begins their alternating-shot turn.) Effective scotch doubles play requires close communication between team partners, especially as to desired cue ball position for the incoming player. Like "english", "scotch" is usually not capitalized in this context. The term is also used in bowling, and may have originated there.

The precise center of the pool table.

To move a ball (usually deliberately) from a safe position, e.g. close to the middle of a cushion or in a cluster, so that it becomes pottable.

This is a shot in snooker where the cue ball follows a struck object into the pocket.

This is a bank in one pocket pool that is sitting at an angle that makes it unsafe to play.

This is playing to a higher winning score than eight in the game of one pocket.

Similar to run out, but more specific to making all required shots from the start of a rack. Also known as also break and run or break and dish.

A term used in snooker for the potting of all the balls that are racked at the beginning of the frame in a single break (run). The minimum total clearance affords 72 points (barring multiple reds being potted on a single stroke), in the pattern of red then yellow repeatedly until all reds are potted, then all of the colour balls. The maximum break is 147 (barring a foul by the opponent immediately before the break began).

This is an object ball that essentially covers up a path necessary for sinking the desired object ball.

This is a player who has the ability to make difficult shots in one pocket, because they are likely proficient at other pool games first.

Cueing and timing the balls well; in good form, where pocketing (potting), safety and clarity of thinking seem to come easily.

A shot where the cue ball must hit the object ball so as to make it travel out of a straight line, at a different angle, toward its destination.

When a player is playing flawlessly, just "cannot miss" and the game seems effortless.

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

Same as follow (top spin).

An imaginary line drawn from the desired path an object ball is to be sent (usually the center of a pocket) and the center of the object ball.

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.

A combination shot, where hitting the first ball rubs it against the center connecting line of two frozen object balls throwing the second out.

A deliberate foul that leaves the balls in a safe position, reducing the risk of giving a frame-winning chance to the opponent. The miss rule in snooker was implemented primarily to discourage the professional fouls.

A pool table where two shims have been placed on the sides of each pocket (in the jaws beneath the cloth), making the pockets "tighter" (smaller). Such tables are "tougher" than unshimmed or single-shimmed tables.