Source : Webster's Revised Unabridged Dictionary (1913)

Reflex \Re"flex\ (r?"fl?ks), a. [L. reflexus, p. p. of
   reflectere: cf. F. r['e]flexe. See {Reflect}.]
   1. Directed back; attended by reflection; retroactive;
      introspective.

            The reflex act of the soul, or the turning of the
            intellectual eye inward upon its own actions. --Sir
                                                  M. Hale.

   2. Produced in reaction, in resistance, or in return.

   3. (Physiol.) Of, pertaining to, or produced by, stimulus or
      excitation without the necessary intervention of
      consciousness.

   {Reflex action} (Physiol.), any action performed
      involuntarily in consequence of an impulse or impression
      transmitted along afferent nerves to a nerve center, from
      which it is reflected to an efferent nerve, and so calls
      into action certain muscles, organs, or cells.

   {Reflex nerve} (Physiol.), an excito-motory nerve. See
      {Exito-motory}.

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}.

Reflex \Re*flex"\ (r?*fl?ks"), v. t. [L. reflexus, p. p. of
   reflectere. See {Reflect}.]
   1. To reflect. [Obs.] --Shak.

   2. To bend back; to turn back. --J. Gregory.

Source : WordNet®

reflex
     n : an automatic instinctive unlearned reaction to a stimulus
         [syn: {instinctive reflex}, {innate reflex}, {inborn
         reflex}, {unconditioned reflex}, {physiological reaction}]

reflex
     adj : without volition or conscious control; "the automatic
           shrinking of the pupils of the eye in strong light"; "a
           reflex knee jerk"; "sneezing is reflexive" [syn: {automatic},
            {reflex(a)}, {reflexive}]