1A person or being that controls everything; one having infinite power.
2Specifically (now chiefly in Jewish usage): God.
3(With capital initials.) A trademark for: one of a series of superhero action figures; a cartoon (or other) character based on one of these figures.
4A person who is exceptionally successful in business.
Late 17th century; earliest use found in John Dryden (1631–1700), poet, playwright, and critic. From master + of + the + universe.