absence of or disregard for an established musical key in a composition
2.
the principles of composition embodying this and providing a radical alternative to the diatonic system
Compare tonality
atonality in American English
(ˌeɪtoʊˈnæləti)
noun
Music
in composition, the organization of tones in which all tones of the chromatic scale have equal importance, without relation to a tonal center or key; the absence of tonality