Tri'o or Tri'ō, n.
(Synop., §130), n. [It., Sp., & Fr. trio, from Lat. tres, tria, three.] 1. Three united; three persons in company or acting together.
The trio were well accustomed to act together, and were linked to each other by ties of mutual interest and advantage. Dickens.
Sense 2. (Mus.) A composition for three parts.