<p><strong>Noun</strong></p><ul><li>Mr.; Sir: a Spanish title prefixed to a man's given name.</li><li>(in Spanish-speaking countries) a lord or gentleman.</li><li>(initial capital letter) an Italian title of address, especially for a priest.</li><li>a person of great importance.</li><li>(in the English universities) a head, fellow, or tutor of a college.</li><li>(in the Mafia) a head of a family or syndicate.</li></ul>