The Collaborative International Dictionary of English v.0.48:
common room \common room\, common-room \common-room\n. a room, usually at a school or university, set aside for the common use of everyone. It usually has comfortable chairs for reading or conversation, and some provision for obtaining refreshments. Syn: . [WordNet 1.5 +PJC]WordNet (r) 3.0 (2006):
common room n 1: a sitting room (usually at school or university)