Pronunciation: (stā'dē-um),[key] —n., —pl.-di•ums, -di•aPronunciation: (-dē-u).[key] 1. a sports arena, usually oval or horseshoe-shaped, with tiers of seats for spectators.
2. an ancient Greek course for foot races, typically semicircular, with tiers of seats for spectators.
3. an ancient Greek and Roman unit of length, the Athenian unit being equal to about 607 feet (185 m).
4. a stage in a process or in the life of an organism.
5. Entomol.stage (def. 11b).