/ Dictionary / Index A ascertain: Meaning and Definition of Find definitions for: as•cer•tain Pronunciation: (as"ur-tān'), [key] — v.t. to find out definitely; learn with certainty or assurance; determine: to ascertain the facts. to make certain, clear, or definitely known. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: ascertain (Thesaurus) ascent ascesis Related Content Daily Word Quiz: paradox Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language