/ Dictionary / Index U undefined: Meaning and Definition of Find definitions for: un•de•fined Pronunciation: (un"di-fīnd'), [key] — adj. without fixed limits; indefinite in form, extent, or application: undefined authority; undefined feelings of sadness. not given meaning or significance, as by a definition; not defined or explained: an undefined term. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: undefined (Thesaurus) undecylenic acid undemonstrative 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