D defs.my
Entry 5 senses · 2 variants Webster, 1913

Unison

/yo͞on'-əs-ən/ · U·ni·son · IPA /ˈjunɪsən/
01 n. Harmony; agreement; concord; union.
  1. 1.
    Harmony; agreement; concord; union.
  2. 2.
    Identity in pitch; coincidence of sounds proceeding from an equality in the number of vibrations made in a given time by two or more sonorous bodies. Parts played or sung in octaves are also said to be in unison, or in octaves.(Mus.)
  3. 3.
    A single, unvaried.[R.]
Phrases & compounds
In unison — in agreement; agreeing in tone; in concord.
02 a. Sounding alone.
  1. 1.
    Sounding alone.[Obs.]
    “[sounds] intermixed with voice, Choral or unison.” Milton.
  2. 2.
    Sounded alike in pitch; unisonant; unisonous; as, unison passages, in which two or more parts unite in coincident sound.(Mus.)