/ Dictionary / Index I insanity: Meaning and Definition of Find definitions for: in•san•i•ty Pronunciation: (in-san'i-tē), [key] — pl. -ties. the condition of being insane; a derangement of the mind. such unsoundness of mind as affects legal responsibility or capacity. (formerly) psychosis. extreme folly; senselessness; foolhardiness. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: insanity (Thesaurus) insanitation insatiable Related Content Daily Word Quiz: sequester Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language