1.NounIdentical pitch between two notes or sounds; the simultaneous playing of notes of identical pitch (or separated by one or more octaves). .mw-parser-output .defdate{font-size:smaller}
"The unison has a pitch ratio of 1:1."
2.NounA sound or note having the same pitch as another, especially when used as the base note for an interval; a unison string.
3.NounThe state of being in harmony or agreement; harmonious agreement or togetherness, synchronisation.
"Everyone moved in unison, but the sudden change in weight distribution capsized the boat."
4.NounTwo or more voices speaking or singing the same words together.