The party against whom an appeal is filed. The appellee usually seeks affirmance of the lower court's decision. By contrast, the appellant is the party who filed the appeal.
Suppose P sues D, and wins. D files an appeal. P is the appellee, and D is the appellant. If D wins the appeal, and P appeals, the roles are reversed. D becomes the appellee, and P is the appellant.
See Appellate Procedure.