/ Dictionary / Index I insufficient: Meaning and Definition of Find definitions for: in•suf•fi•cient Pronunciation: (in"su-fish'unt), [key] — adj. not sufficient; lacking in what is necessary or required: an insufficient answer. deficient in force, quality, or amount; inadequate: insufficient protection. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: insufficient (Thesaurus) insufficiency insufflate Related Content Daily Word Quiz: acquiesce Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language