tri·um·vir (trī-ŭm'vər) n.
pl.tri·um·virs or tri·um·vi·ri (-və-rī')
One of three men sharing public administration or civil authority in ancient Rome.
One of three people sharing public administration or civil authority.
[Middle English, from Latin, back-formation from triumvirī, board of three, from trium virum, of three men : trium, genitive pl. of trēs, three; see trei- in Indo-European roots + virum, archaic genitive pl. of vir, man; see wī-ro- in Indo-European roots.] tri·um'vi·ral adj.
"one of three men in the same office or of the same authority," 1579, from L. triumvir, from Old L. phrase trium virum, genitive plural of tres viri "three men," from tres "three" + viri, plural of vir "man" (see virile). Triumvirate is from 1584.