- coincidence in pitch of two or more musical tones, voices, etc.
- the musical interval of a perfect prime.
- the performance of musical parts at the same pitch or at the octave.
- a sounding together in octaves, especially of male and female voices or of higher and lower instruments of the same class.
- a process in which all elements behave in the same way at the same time; simultaneous or synchronous parallel action: to march in unison.
- in unison, in perfect accord; corresponding exactly: My feelings on the subject are in unison with yours.
- the interval between two sounds of identical pitch
- (modifier)played or sung at the same pitchunison singing
- complete agreement; harmony (esp in the phrase in unison)
- (in Britain) a trade union representing local government, health care, and other workers: formed in 1993 by the amalgamation of COHSE, NALGO, and NUPE
1570s, from Middle French unisson “unison, accord of sound” (16c.), from Medieval Latin unisonus “having one sound, sounding the same,” from Late Latin unisonius “in immediate sequence in the scale, monotonous,” from Latin uni- “one” (see one) + sonus “sound” (see sound (n.1)). Sense of “harmonious agreement” is first attested 1640s.
In complete agreement, harmonizing exactly. For example, Their opinion was in unison with ours. [Early 1800s]
Saying the same thing at the same time, simultaneously, as in The whole class answered in unison. [Late 1800s] Both usages allude to the unison of music, a single identical pitch.