O*de"on (?), n. [NL., fr. Gr. &?;, fr. &?;: cf.F. odéon. See Ode.] A kind of theater in ancient Greece, smaller than the dramatic theater and roofed over, in which poets and musicians submitted their works to the approval of the public, and contended for prizes; -- hence, in modern usage, the name of a hall for musical or dramatic performances.