ca·stra·to 
(kă-strätō, kə-)
(kă-strätō, kə-)n. pl. ca·stra·ti (-tē) or ca·stra·tos
A male singer castrated before puberty so as to retain a soprano or alto voice.
[Italian, from Latin castrātus, past participle of castrāre, to castrate; see CASTRATE.]