The Collaborative International Dictionary of English v.0.48:

coatroom \coatroom\ n.
   a room where coats and other articles can be left
   temporarily; -- called also cloakroom.

   Syn: cloakroom.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

coatroom
    n 1: a room where coats and other articles can be left
         temporarily [syn: cloakroom, coatroom]