Pronunciation: (trē'ō), [key]
1. a musical composition for three voices or instruments.
2. a company of three singers or players.
3. any group of three persons or things.
4. a subordinate division of a minuet, scherzo, march, etc., usually in a contrasted key and style (perhaps originally written for three instruments or in three parts).
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.