noun

• (formal, usually italicized) The reigning emperor; male equivalent of Imperatrix
  "By a law of the tribunes L. Marius and M. Cato penalties were imposed upon all Imperatores who should be found guilty of having made false returns to the senate, and it was ordained that so soon as they returned to the city they should be required to attest the correctness of such documents upon oath before the city quaestor. […] But to compensate in some degree for what was then taken away, the custom was introduced of bestowing what were Triumphalia Ornamenta, that is, permission to receive the titles bestowed upon and to appear in public with the robes worn by the Imperatores of the commonwealth when they triumphed, and to bequeath to their descendants triumphal statues."