Victorinus (Caius Marius Victorinus Afer)vĭktərĪˈnəs, fl. 361, Roman grammarian, b. Africa. He became renowned as a teacher of rhetoric in Rome and as an advocate of Neoplatonism. Becoming a Christian in his later life, he was forbidden to teach by Emperor Julian. His works include a book on definitions, a treatise on Cicero's De inventione, an unoriginal grammar, several tracts against Arianism, and some Pauline commentaries. Some hymns and several other treatises have been attributed to him.