As a Noun: 1. A building with a stage on which plays and other entertainments are performed. English = theatre. 2. The activity of acting in, producing, and writing plays. English = theatre. As a Verb or Adjective: 1. To belong to or relate to the theatre. English = (be) theatrical. 2. Of behaviour, to be exaggerated, unnatural, and done deliberately for effect. English = (be) theatrical.