Opĭlĭus: i, m.,I a Roman surname.I Aurelius Opilius, a grammarian and author, Suet. Gram. 6.—II Another Aurelius Opilius, a physician, Plin. 28, 4, 7, § 38.—III M. Opilius Severus Macrinus, emperor of Rome, A. D. 218, Eutr. 8, 21.