tri·plet / ˈtriplit/ • n. 1. (usu. triplets) one of three children or animals born at the same birth.2. a set or succession of three similar things. ∎  Mus. a group of three equal notes to be performed in the time of two or four. ∎  a set of three rhyming lines of verse.3. Physics & Chem. an atomic or molecular state characterized by two unpaired electrons with parallel spins. ∎  a group of three associated lines close together in a spectrum or electrophoretic gel.

triplet. Group of 3 notes, or notes and rests, equal in time-value, written where a group of 2 notes is suggested by time signature. Usually indicated by adding numeral 3 above each group.