The Collaborative International Dictionary of English v.0.48:

Gladiator \Glad"i*a`tor\, n. [L., fr. gladius sword. See
   Glaive.]
   1. Originally, a swordplayer; hence, one who fought with
      weapons in public, either on the occasion of a funeral
      ceremony, or in the arena, for public amusement.
      [1913 Webster]

   2. One who engages in any fierce combat or controversy.
      Gladiatorial

WordNet (r) 3.0 (2006):

gladiator
    n 1: (ancient Rome) a professional combatant or a captive who
         entertained the public by engaging in mortal combat
    2: a professional boxer [syn: prizefighter, gladiator]