Early Music. A part pitched higher than the treble and quatreble; a high-pitched song or voice. Now historical.
There is now some doubt as to whether the word was ever used as a strictly technical term, though there have been various conjectures as to an exact pitch, interval, or voice which it might have represented..
Origin
Late Middle English; earliest use found in Geoffrey Chaucer (c1340–1400), poet and administrator. Irregularly from quin- (in classical Latin quīnque five: see quinque-) + -ible.