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
See atonality in American Heritage Dictionary 4
nounpl.a·to·nal·i·ties Music
The absence of a tonal center and of harmonies derived from a diatonic scale corresponding to such a center; lack of tonality.
A style of composition that lacks such a tonal center and its derived harmonies.