The Collaborative International Dictionary of English v.0.48:

Contender \Con*tend"er\, n.
   One who contends; a contestant.
   [1913 Webster]

WordNet (r) 3.0 (2006):

contender
    n 1: the contestant you hope to defeat; "he had respect for his
         rivals"; "he wanted to know what the competition was doing"
         [syn: rival, challenger, competitor, competition,
         contender]

Moby Thesaurus II by Grady Ward, 1.0:

61 Moby Thesaurus words for "contender":
   battler, belligerent, belted knight, bickerer, blade, bravo,
   brawler, bully, bullyboy, combatant, competitor, contestant,
   corrival, disputant, duelist, emulator, enforcer, entrant, fencer,
   feuder, fighter, fighting cock, foilsman, gamecock, gladiator,
   goon, gorilla, hatchet man, hood, hoodlum, hooligan, jouster,
   knight, militant, player, plug-ugly, quarreler, rioter, rival,
   rough, rowdy, ruffian, sabreur, scrapper, scuffler, squabbler,
   strong arm, strong-arm man, strong-armer, struggler, swashbuckler,
   sword, swordplayer, swordsman, the field, thug, tilter, tough,
   tussler, vier, wrangler