The Collaborative International Dictionary of English v.0.48:

Skater \Skat"er\, n.
   1. One who skates.
      [1913 Webster]

   2. (Zool.) Any one of numerous species of hemipterous insects
      belonging to Gerris, Pyrrhocoris, Prostemma, and
      allied genera. They have long legs, and run rapidly over
      the surface of the water, as if skating.
      [1913 Webster]

WordNet (r) 3.0 (2006):

skater
    n 1: someone who skates