threesome
n.a group of three people who do something together. It is often used to describe three people having sex together, but it can also mean a group of three in sports or music.
n.a group of three people engaged in a joint activity. While frequently used to describe a sexual encounter involving three participants, it also applies to trios in golf or musical ensembles.
“The three friends formed a threesome for the golf tournament.”
“After their third partner joined the venture, the duo became a productive threesome that managed the firm effectively.”
“The narrative explores the shifting dynamics of a domestic threesome, tracing how the introduction of a third party destabilizes the original couple's long-standing emotional equilibrium.”
Commonly used in both casual social contexts and specific sexual contexts; the latter is the dominant modern association.
From three + -some.
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.