Lewis & Short

compĕtītor, ōris, m. [competo],

  1. I. a rival, competitor (in good prose); in gen., Cic. Off. 1, 12, 38; id. Planc. 4, 9; id. Att. 1, 1, 1; Liv. 6, 41, 2; 37, 57, 15; Quint. 3, 7, 2; 7, 1, 29; 9, 2, 97; Suet. Caes. 13; 19; Dig. 50, 2, 3, § 2.
  2. II. Esp., a plaintiff, Cod. Th. 10, 9, 2.