tri·um·vi·rate / trīˈəmvərit; -ˌrāt/ • n. 1. (in ancient Rome) a group of three men holding power, in particular (the First Triumvirate) the unofficial coalition of Julius Caesar, Pompey, and Crassus in 60 bc and (the Second Triumvirate) a coalition formed by Antony, Lepidus, and Octavian in 43 bc. ∎  a group of three powerful or notable people or things existing in relation to each other: a triumvirate of three former executive vice presidents.2. the office of triumvir in ancient Rome.

tri·um·vir / trīˈəmvər/ • n. (pl. -virs or -vi·ri / -vəˌrī/ ) (in ancient Rome) each of three public officers jointly responsible for overseeing any of the administrative departments.DERIVATIVES: tri·um·vi·ral / -rəl/ adj.

triumvir (Rom. hist.) one of a board of three magistrates. XVI. — L., sg. deduced from pl. triumvirī, back-formation from trium virōrum, g. pl. of trēs virī three men.
So triumvirate (-ATE1) XVI. — L. trium virātus.

Triumvirate

a group, party, or association of three leaders, 1601.