Source : Webster's Revised Unabridged Dictionary (1913)

Apperception \Ap`per*cep"tion\, n. [Pref. ad- + perception: cf.
   F. apperception.] (Metaph.)
   The mind's perception of itself as the subject or actor in
   its own states; perception that reflects upon itself;
   sometimes, intensified or energetic perception. --Leibnitz.
   Reid.

         This feeling has been called by philosophers the
         apperception or consciousness of our own existence.
                                                  --Sir W.
                                                  Hamilton.

Source : WordNet®

apperception
     n : the process whereby perceived qualities of an object are
         related to past experience