Real Dictionary

gladiator
countable noun: In the time of the Roman Empire, a gladiator was a man who had to fight against other men or wild animals in order to entertain an audience.
countable noun: You can refer to a sports player or a performer as a gladiator in order to emphasize how brave or dangerous their actions are.

gladiator in American English
in ancient Rome, a man who fought other men or animals with a sword or other weapon in an arena, for the entertainment of spectators: gladiators were slaves, captives, or paid performers
noun: a person, often a slave or captive, who was armed with a sword or other weapon and compelled to fight to the death in a public arena against another person or a wild animal, for the entertainment of the spectators

gladiator in British English
noun: (in ancient Rome and Etruria) a man trained to fight in arenas to provide entertainment