1. circular building: a round or oval building without a roof that has a central open space surrounded by tiers of seats, especially one used by the ancient Romans for public entertainments
2. place for sports: a large enclosure where sporting activities or public entertainments take place
3. seating for spectators: a gallery of seats arranged in semicircular tiers for the audience in a theater or lecture room
4. lecture room: a lecture hall or operating room where seating is arranged in semicircular tiers
[Mid-14th century. Via Latin< Greek amphitheatron, "theater on both sides" (because the typical classical Greek theater had seating on one side only) < theatron (see theater)]
