- the male sovereign or supreme ruler of an empire: the emperors of Rome.
- Chiefly British. a size of drawing or writing paper, 48 × 72 inches (122 × 183 cm).
- a monarch who rules or reigns over an empire
- Also called: emperor moth any of several large saturniid moths with eyelike markings on each wing, esp Saturnia pavonia of EuropeSee also giant peacock moth
- See purple emperor
early 13c., from Old French empereor (accusative; nominative emperere; Modern French empereur), from Latin imperiatorem (nominative imperiator) “commander, emperor,” from past participle stem of imperare “to command” (see empire).
Originally a title conferred by vote of the Roman army on a successful general, later by the Senate on Julius and Augustus Caesar and adopted by their successors except Tiberius and Claudius. In the Middle Ages, applied to rulers of China, Japan, etc.; only non-historical European application in English was to the Holy Roman Emperors (who in German documents are called kaiser), from late 13c., until in 1804 Napoleon took the title “Emperor of the French.”