Suetonius Syllabification: (Sue·to·ni·us)Pronunciation: /so͞oəˈtōnēəs, swēˈtō-/Definition of Suetonius (circa 69-circa 150), Roman biographer and historian; full name Gaius Suetonius Tranquillus. His surviving works include Lives of the Caesars. Suetonius in other Oxford dictionaries Definition of Suetonius in the British & World English dictionary