threesome
n. 三倍的; 三人一组; 三人的竞赛; 一人对两人的比赛
A threesome is a group of three people.
1. the cardinal number that is the sum of one and one and one
2. three people considered as a unit
By then the threesome was already past its prime.
到聚会时三人都已经超过了做研究的最佳时期.