appellor

from The Collaborative International Dictionary of English v.0.48
Appellor \Ap`pel*lor"\ ([a^]p`p[e^]l*l[^o]r"), n. [OF. apeleur,
   fr. L. appellator, fr. appellare.] (Law)
   (a) The person who institutes an appeal, or prosecutes
       another for a crime. --Blackstone.
   (b) One who confesses a felony committed and accuses his
       accomplices. --Blount. --Burrill.
       [1913 Webster]

   Note: This word is rarely or never used for the plaintiff in
         appeal from a lower court, who is called the
         {appellant}. Appellee is opposed both to {appellant}
         and appellor.
         [1913 Webster]
    
from Bouvier's Law Dictionary, Revised 6th Ed (1856)
APPELLOR. A criminal who accuses his accomplices; one who challenges a jury.
    

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