The Collaborative International Dictionary of English v.0.48:

Triskelion \Tris*kel"i*on\, or Triskele \Tris"kele\, n. [Gr. ?
   three-legged. See Tri-; Isosceles.]
   A figure composed of three branches, usually curved,
   radiating from a center, as the figure composed of three
   human legs, with bent knees, which has long been used as a
   badge or symbol of Sicily and of the Isle of Man.
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

triskelion
    n 1: a figure consisting of three stylized human arms or legs
         (or three bent lines) radiating from a center [syn:
         triskelion, triskele]