<p><strong>Noun</strong></p><ul><li>the lowest female voice; contralto.</li><li>the highest male voice; countertenor.</li><li>a singer with such a voice.</li><li>a musical part for such a voice.</li><li>the second highest of the four parts of a mixed vocal chorus, or the voices or persons singing this part.</li><li>the second highest instrument in a family of musical instruments, as the viola in the violin family or the althorn in the cornet family.</li></ul><p><strong>Adjective</strong></p><ul><li>of, relating to, or having the tonal range of the alto.</li><li>(of a musical instrument) second highest in a family of musical instruments: alto saxophone.</li></ul>