The Collaborative International Dictionary
Sopranist \So*pra"nist\, n. (Mus.) A treble singer.
Wiktionary
n. a male soprano singer
Wikipedia
A sopranist (also, sopranista or male soprano) is a male singer who is able to sing in the vocal tessitura of a soprano usually through the use of falsetto vocal production. This voice type is a specific kind of countertenor. In rare cases an adult man may be able to sing in the soprano range using his normal or modal voice and not falsetto due to endocrinological reasons, like Radu Marian, or as a result of a larynx that has not completely developed as in the case of Michael Maniaci.
Usage examples of "sopranist".
Rossini and Donizetti have revealed enough genius in some of their sparkling melodies to make it probable that, if they had not so often stooped to the level of a taste corrupted by the sopranists, they might have raised the public to a higher standard of musical taste.