Source : Webster's Revised Unabridged Dictionary (1913)

Trochal \Tro"chal\, a. [From Gr. ? a wheel.] (Zo["o]l.)
   Resembling a wheel.

   {Trochal disk} (Zo["o]l.), the cephalic disk of a rotifer. It
      is usually surrounded by a fringe of cilia.