The Collaborative International Dictionary of English v.0.48:

Lavatory \Lav"a*to*ry\, a.
   Washing, or cleansing by washing.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Lavatory \Lav"a*to*ry\, n.; pl. Lavatories. [L. lavatorium:
   cf. lavatoire. See Lave to wash, and cf. Laver.]
   1. A place for washing.
      [1913 Webster]

   2. A basin or other vessel for washing in.
      [1913 Webster]

   3. A wash or lotion for a diseased part.
      [1913 Webster]

   4. A place where gold is obtained by washing.
      [1913 Webster]

   5. A room containing one or more sinks for washing, as well
      as one or more toilet fixtures; also called bathroom,
      toilet, and sometimes commode. Commode and toilet may
      refer to a room with only a toilet fixture, but without a
      sink.

   Syn: toilet, lavatory, can, facility, john, privy, bathroom.
        [WordNet 1.5 +PJC]

WordNet (r) 3.0 (2006):

lavatory
    n 1: a room or building equipped with one or more toilets [syn:
         toilet, lavatory, lav, can, john, privy,
         bathroom]
    2: a bathroom sink that is permanently installed and connected
       to a water supply and drainpipe; where you can wash your
       hands and face; "he ran some water in the basin and splashed
       it on his face" [syn: washbasin, basin, washbowl,
       washstand, lavatory]
    3: a toilet that is cleaned of waste by the flow of water
       through it [syn: flush toilet, lavatory]

Moby Thesaurus II by Grady Ward, 1.0:

78 Moby Thesaurus words for "lavatory":
   WC, aquamanile, automatic dishwasher, backhouse, bagnio, balneae,
   balneum, basement, basin, bath, bathhouse, bathroom, baths,
   bathtub, bidet, bog, caldarium, can, closet, comfort station,
   convenience, crapper, dishpan, dishwasher, earth closet, equipment,
   ewer, finger bowl, head, john, johnny, johnny house, kitchen sink,
   latrine, lavabo, loo, mikvah, necessary, outhouse, piscina,
   powder room, privy, public baths, rest room, sauna, shower,
   shower bath, shower curtain, shower head, shower room,
   shower stall, showers, sink, spa, steam room, sudarium, sudatorium,
   sweat room, tepidarium, thermae, toilet, toilet room, tub, urinal,
   wash barrel, wash boiler, washbasin, washbowl, washdish, washer,
   washing machine, washing pot, washpot, washroom, washstand,
   washtub, water closet, watering place