/ Dictionary / Index S supposal: Meaning and Definition of Find definitions for: sup•pos•al Pronunciation: (su-pō'zul), [key] — n. the act of supposing. something that is supposed; conjecture or notion. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: supposal (Thesaurus) support system suppose Related Content Daily Word Quiz: secular Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language