/ Dictionary / Index M mutual aid: Meaning and Definition of Find definitions for: mu'tual aid' Pronunciation: [key] the cooperative as opposed to the competitive factors operating in the development of society. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. mutual Mutual Assured Destruction Related Content Daily Word Quiz: abscond Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language