Set ( poker )

1) In hold 'em and stud, three of a kind. To flop a set in hold 'em means that (most often) one started with a pair and one of those cards was among the flop (the first three community cards). Less often it means a pair was among the flop and the player had another card of that rank in the hole.
2) Four of a kind, particularly as part of the phrase set of fours.
3) Arrange the two hands that are made out of the seven cards dealt each player in pai gow poker.