—n. 1. the lowest female voice; contralto.
2. the highest male voice; countertenor.
3. a singer with such a voice.
4. a musical part for such a voice.
5. the second highest of the four parts of a mixed vocal chorus, or the voices or persons singing this part.
6. the second highest instrument in a family of musical instruments, as the viola in the violin family or the althorn in the cornet family.
—adj. 1. of, pertaining to, or having the tonal range of the alto.
2. (of a musical instrument) second highest in a family of musical instruments: alto saxophone.