n. 四人的一组, 四人对抗赛

a. 四人做的, 由四组成的

Foursome \Four"some\, 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]


Foursome \Four"some\ (f[=o]r"s[u^]m), a. [Four + 2d -some.]
Consisting of four; requiring four participants. [Scot. or
Golf]
[Webster 1913 Suppl.]