Cassius, Gaius Syllabification: (Cas·sius, Gaius)Pronunciation: /ˈkasēəs, ˈkaSHəs/Definition of Cassius, Gaius (died 42 bc), Roman general; full name Gaius Cassius Longinus. He was one of the leaders of the conspiracy in 44 bc to assassinate Julius Caesar. Cassius, Gaius in other Oxford dictionaries Definition of Cassius, Gaius in the British & World English dictionary