A triumvirate is a group of three people who work together, especially when they are in charge of something. the triumvirate of women who worked together on the TV dramatisation of the novel. a group of three very powerful people (triumviratus, from triumviri , from trium virum ). In ancient Rome, usually a board of three officials who assisted higher magistrates in judicial functions, oversaw festival banquets, or ran the mint. The First Triumvirate (60 BC) of Pompey, Julius Caesar, and Crassus was an informal group of three strong leaders with no sanctioned powers. The Second Triumvirate (43 BC), consisting of Mark Antony, Lepidus, and Octavian (later Augustus) formally tresviri rei publicae constituendae ("triumvirate for organizing the state") held absolute dictatorial power