twelve-tone definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
Music designating or of a system or technique of serial composition, developed by Arnold Schönberg, in which the twelve tones of the chromatic scale are arranged into some arbitrary, fixed succession (tone row) which then forms a basis for development
twelve-tone definition by American Heritage Dictionary
Relating to, consisting of, or based on an arrangement of the 12 chromatic tones.