Full Definition of GLADIATOR. 1. : a person engaged in a fight to the death as public entertainment for ancient Romans. 2. : a person engaging in a public fight or controversy.3. : a trained fighter; especially: a professional boxer.â gladÂ·iÂ·aÂ·toÂ·riÂ·al \Ëgla-dÄ-É-ËtoÌr-Ä-Él\ adjective.ull Definition of GLADIATOR. 1. : a person engaged in a fight to the death as public entertainment for ancient Romans. 2. : a person engaging in a public fight or controversy. 3.