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).
Origin: 1715–25; < Italian, equivalent to tri-tri- + (du)otwo