/ Dictionary / Index S substantiate: Meaning and Definition of Find definitions for: sub•stan•ti•ate Pronunciation: (sub-stan'shē-āt"), [key] — -at•ed, -at•ing. to establish by proof or competent evidence: to substantiate a charge. to give substantial existence to: to substantiate an idea through action. to affirm as having substance; give body to; strengthen: to substantiate a friendship. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: substantiate (Thesaurus) substantia nigra substantival Related Content Daily Word Quiz: neologism Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language