adj. Having four sides.
Syn. -- quadrilateral. [ WordNet 1.5 ]

a. [ Four + core, n. ] Four times twenty; eighty. [ 1913 Webster ]

n. The product of four times twenty; eighty units or objects. [ 1913 Webster ]

a. [ Four + 2d -some. ] Consisting of four; requiring four participants. [ Scot. or Golf ] [ Webster 1913 Suppl. ]

n. 1. (Golf) A game between four players, with two on each side and each side playing but one ball, the partners striking alternately. It is called a mixed foursome when each side consists of a man and a woman. [ Webster 1913 Suppl. ]

2. A group of four people or objects; as, we need another player to make a foursome for bridge. [ PJC ]

a. Having four sides and four equal angles. Sir W. Raleigh. [ 1913 Webster ]