/ Dictionary / Index M mental retardation: Meaning and Definition of Find definitions for: men'tal retarda'tion Pronunciation: [key] a developmental disorder characterized by a subnormal ability to learn and a substantially low IQ. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. mental reservation mental telepathy Related Content Daily Word Quiz: cautious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language