A situation where a player has fouled, leaving the opponent snookered. In UK eight-ball this would normally give the opponent the option of one of two plays: (1) ball-in-hand with two shots; (2) being allowed to contact, or even pot, a ball other than one from his/her set from the snookered position (although the black may not be potted), with the loss of the first shot. In addition, some variations of the game allow the player to pot one of the opposition's balls, on the first visit only, without the loss of a "free shot".
In snooker it allows a player to call any ball as the ball she/he would have wanted to play, potting it for the same number of points, or the opponent can be put back in without the same privilege, having to play the ball snookered on. The definition of snooker on this occasion means the opponent cannot strike both extreme edges of the object ball (or a cluster of touching balls).