<p><strong>Noun</strong></p><ul><li>plural nemeses:<ul><li>something that a person cannot conquer, achieve, etc.: The performance test proved to be my nemesis.</li><li>an opponent or rival whom a person cannot best or overcome.</li><li>(initial capital letter) Classical Mythology: the goddess of divine retribution.</li><li>an agent or act of retribution or punishment.</li></ul></li></ul>