/ Dictionary / Index D demented: Meaning and Definition of Find definitions for: de•ment•ed Pronunciation: (di-men'tid), [key] — adj. crazy; insane; mad. affected with dementia. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: demented (Thesaurus) dement démenti Related Content Daily Word Quiz: impetuous Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language