OXFORD DICTIONARY
theatre, n. (US theater)
1 a a building or outdoor area for dramatic performances. b a cinema.
2 a the writing and production of plays. b effective material for the stage (makes good theatre).
3 a room or hall for lectures etc. with seats in tiers.
4 Brit. an operating theatre.
5 a a scene or field of action (the theatre of war). b (attrib.) designating weapons intermediate between tactical and strategic (theatre nuclear missiles).
6 a natural land-formation in a gradually rising part-circle like ancient Greek and Roman theatres.
theatre-goer a frequenter of theatres. theatre-going frequenting theatres. theatre-in-the-round a dramatic performance on a stage surrounded by spectators. theatre sister a nurse supervising the nursing team in an operating theatre.
ME f. OF t(h)eatre or f. L theatrum f. Gk theatron f. theaomai behold
THESAURUS
theatre
acting, area, arena, auditorium, coliseum, drama, dramaturgy, hippodrome, histrionics, melodrama, opera house, performance, performing, playhouse, scene, setting, show business, stagecraft, staginess, the boards, the stage, theatrics