society > authority > rule or government > ruler or governor > sovereign ruler or monarch > emperor > [noun] > of eastern or western Roman Empire (2)
The (male) sovereign ruler of an empire. Cf. empress, n. 1. Frequently as a title (often with the). historical. The sovereign ruler of the Roman…
historical. The sovereign of the undivided Roman Empire (Roman Empire, n. 1), or of one of the Western or Eastern empires; = emperor, n. 1a.