/ Dictionary / Index I ill-defined: Meaning and Definition of Find definitions for: ill-de•fined Pronunciation: (il'di-fīnd'), [key] — adj. badly or inadequately defined; vague: He confuses the reader with ill-defined terms and concepts. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: ill-defined (Thesaurus) ill-considered ill-disposed Related Content Daily Word Quiz: fabricate Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language