The Collaborative International Dictionary of English v.0.48:

Trochlear \Troch"le*ar\, n. [L. trochlea block or pulley.]
   (Anat.)
   Shaped like, or resembling, a pulley; pertaining to, or
   connected with, a trochlea; as, a trochlear articular
   surface; the trochlear muscle of the eye.
   [1913 Webster]

   Trochlear nerve. See Pathetic nerve, under Pathetic.
      [1913 Webster]

WordNet (r) 3.0 (2006):

trochlear nerve
    n 1: either of the two cranial nerves on either side that
         control the superior oblique muscles of the eyes [syn:
         trochlear, trochlear nerve, trochlearis, fourth
         cranial nerve]