<p><strong>Adjective</strong></p><ul><li>happening by chance or accident; not planned; unexpected: an accidental meeting.</li><li>Synonyms: unintentional</li><li>Antonyms: contrived, planned</li><li>nonessential; incidental; subsidiary: accidental benefits.</li><li>Music: relating to or indicating sharps, flats, or naturals.</li></ul><p><strong>Noun</strong></p><ul><li>a nonessential or subsidiary circumstance, characteristic, or feature.</li><li>Music: a sign placed before a note indicating a chromatic alteration of its pitch.</li></ul>