In a dangerous circumstance A player whose cue ball (the ball that strikes the other balls) is behind the 8 ball is unlikely to make any shots in certain pool or billiards games. If this occurs, the person who shot the ball can either shoot again or call a foul. If he shoots again and fails, then there is no limit to how many times he can be defeated by the same shot. The term comes from pool, where eight balls are used, with one ball called the cue ball. When the cue ball is struck, all the other balls are hit. So if the 8 ball is struck but not put into play, that means that no game can be won or lost with that shot. However, if some other ball is sunk using information obtained from the 8 ball strike, then that ball would become the cue ball for future shots. For example, if ball #8 is struck but not sunk, that means that no score can be made with that shot. However, if we get information from that shot that tells us which way ball #1 is going, then we could line up to shoot it perfectly to match that direction. Or if we wanted to confuse things, we could try to sink both balls on the next shot! This situation arises very often in practice games.