The Collaborative International Dictionary of English v.0.48:

Washer \Wash"er\, n. [AS. w[ae]scere.]
   1. One who, or that which, washes.
      [1913 Webster]

   2. A ring of metal, leather, or other material, or a
      perforated plate, used for various purposes, as around a
      bolt or screw to form a seat for the head or nut, or
      around a wagon axle to prevent endwise motion of the hub
      of the wheel and relieve friction, or in a joint to form a
      packing, etc.
      [1913 Webster]

   3. (Plumbing) A fitting, usually having a plug, applied to a
      cistern, tub, sink, or the like, and forming the outlet
      opening.
      [1913 Webster]

   4. (Zool.) The common raccoon.
      [1913 Webster]

   5. (Zool.) Same as Washerwoman, 2. [Prov. Eng.]
      [1913 Webster]

WordNet (r) 3.0 (2006):

washer
    n 1: someone who washes things for a living
    2: seal consisting of a flat disk placed to prevent leakage
    3: a home appliance for washing clothes and linens automatically
       [syn: washer, automatic washer, washing machine]

Moby Thesaurus II by Grady Ward, 1.0:

45 Moby Thesaurus words for "washer":
   aquamanile, automatic dishwasher, basin, bath, bathtub, bidet,
   dishpan, dishwasher, dishwiper, dry cleaner, ewer, finger bowl,
   kitchen sink, launderer, laundress, laundryman, laundrywoman,
   lavabo, lavatory, piscina, pot-walloper, scullery maid, scullion,
   shower, shower bath, shower curtain, shower head, shower room,
   shower stall, showers, sink, tub, wash barrel, wash boiler,
   washbasin, washbowl, washdish, washerman, washerwife, washerwoman,
   washing machine, washing pot, washpot, washstand, washtub