/ Dictionary / Index A assumpsit: Meaning and Definition of Find definitions for: as•sump•sit Pronunciation: (u-sump'sit), [key] — n. Law. a legal action for a breach of contract or promise not under seal. an actionable promise. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. assuming assumption Related Content Daily Word Quiz: blithesome Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language