Source : Webster's Revised Unabridged Dictionary (1913)

Reflex \Re"flex\ (r?"fl?ks; formerly r?*fl?ks"), n. [L. reflexus
   a bending back. See {Reflect}.]
   1. Reflection; the light reflected from an illuminated
      surface to one in shade.

            Yon gray is not the morning's eye, 'Tis but the pale
            reflex of Cynthia's brow.             --Shak.

            On the depths of death there swims The reflex of a
            human face.                           --Tennyson.

   2. (Physiol.) An involuntary movement produced by reflex
      action.

   {Patellar reflex}. See {Knee jerk}, under {Knee}.

Source : WordNet®

patellar reflex
     n : a reflex extension of the leg resulting from a sharp tap on
         the patellar tendon [syn: {knee jerk}, {knee-jerk reflex}]