The Collaborative International Dictionary of English v.0.48:

bathhouse \bathhouse\ n.
   1. a building containing dressing rooms for bathers.

   Syn: bathing machine.
        [WordNet 1.5]

   2. a building containing public baths.

   Syn: bagnio.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

bathhouse
    n 1: a building containing dressing rooms for bathers [syn:
         bathhouse, bathing machine]
    2: a building containing public baths [syn: bathhouse,
       bagnio]

Moby Thesaurus II by Grady Ward, 1.0:

21 Moby Thesaurus words for "bathhouse":
   bagnio, balneae, balneum, bath, bathroom, baths, caldarium,
   lavatory, mikvah, public baths, rest room, sauna, spa, steam room,
   sudarium, sudatorium, sweat room, tepidarium, thermae, washroom,
   watering place