Specifically, the ruler of the Holy Roman Empire; the world-monarch.
A large, relatively valuable marble in children's games.
Any of various butterflies of the subfamily Charaxinae.
Any of various large dragonflies of the cosmopolitan genus Anax.
An emperor penguin.
The fourth trump or major arcana card of the tarot deck.
The male monarch or ruler of an empire.
Any monarch ruling an empire, irrespective of gender, with "empress" contrasting to mean the consort of an emperor.
Any fish of the family Lethrinidae.
In certain nations the highest military rank, ranking below only the commander in chief; now essentially disused.