Breadcrumb Home > Dictionary > Index A assertion: Meaning and Definition of Find definitions for: as•ser•tion Pronunciation: (u-sûr'shun), [key] — n. a positive statement or declaration, often without support or reason: a mere assertion; an unwarranted assertion. an act of asserting. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: assertion (Thesaurus) asserted assertive ✖ Related Content Daily Word Quiz: centrifugal Analogy of the Day: Today’s Analogy Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language