n. Supreme power in governing; imperial power; dominion; sovereignty.n. The country, region, or union of states or territories under the jurisdiction and dominion of an emperor or other powerful sovereign or government; usually, a territory of greater extent than a kingdom, which may be, and often is, of small extent: as, the Roman or the Russian empire.n. Supreme control; governing influence; rule; sway: as, the empire of reason or of truth.n. Synonyms Sway, dominion, rule, reign, government, supremacy.