The Collaborative International Dictionary of English v.0.48:

Caster \Cast"er\, n.
   1. One who casts; as, caster of stones, etc.; a caster of
      cannon; a caster of accounts.
      [1913 Webster]

   2. A vial, cruet, or other small vessel, used to contain
      condiments at the table; as, a set of casters.
      [1913 Webster]

   3. A stand to hold a set of cruets.
      [1913 Webster]

   4. A small wheel on a swivel, on which furniture is supported
      and moved.
      [1913 Webster]

WordNet (r) 3.0 (2006):

caster
    n 1: a worker who casts molten metal into finished products
    2: a shaker with a perforated top for sprinkling powdered sugar
       [syn: caster, castor]
    3: a pivoting roller attached to the bottom of furniture or
       trucks or portable machines to make them movable [syn:
       caster, castor]