1) Composition for three 2) Deuce-ace 3) Digit 4) Figure 5) Leash 6) Tercet 7) Ternary 8) Ternion 9) Three 10) Threesome 11) Tierce 12) Trey 13) Triad 14) Trine 15) Trinity 16) Trio 17) Triplet 18) Troika 19) Vocal trio 1) Tercet 2) Ternion 3) Threesome 4) Trey 5) Triad 6) Trine 7) Trinity 8) Trio 9) Triplet 
Ter·zet'to noun [ Italian , dim. of terzo the third, Latin tertius . See Tierce .] (Mus.) A composition in three voice parts; a vocal (rarely an instrumental) trio. 
A terzetto is a musical composition in three voice parts forming usually a vocal trio.