The Collaborative International Dictionary of English v.0.48:

Appellee \Ap`pel*lee"\, n. [F. appel['e], p. p. of appeler, fr.
   L. appellare.] (Law)
   (a) The defendant in an appeal; -- opposed to appellant.
   (b) The person who is appealed against, or accused of crime;
       -- opposed to appellor. --Blackstone.
       [1913 Webster]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

APPELLEE, practice. The party in a cause against whom an appeal has been
taken.