n. & adj.
--n.
1. Mus. a coincidence in pitch of sounds or notes. b this regarded as an interval.
2 Mus. a combination of voices or instruments at the same pitch or at pitches differing by one or more octaves (sang in unison).
3 agreement, concord (acted in perfect unison).
--adj. Mus. coinciding in pitch.
Phrases and idioms:
unison string a string tuned in unison with another string and meant to be sounded with it.
Derivatives:
unisonant adj. unisonous adj.
Etymology: OF unison or LL unisonus (as UNI-, sonus SOUND(1))