Sem'i·cho`rus noun (Mus.) A half chorus; a passage to be sung by a selected portion of the voices, as the female voices only, in contrast with the full choir. Found on http://www.encyclo.co.uk/webster/S/63
In music a semichorus is a half chorus or a passage to be sung by a selected portion of the voices, as for example by the female voices only, in contrast with the full choir. Found on http://www.probertencyclopaedia.com/browse/VS.HTM