/ Thesaurus / M Synonyms of mass deficiency Find synonyms for: Noun1. mass defect, mass deficiency, massusage: the amount by which the mass of an atomic nucleus is less than the sum of the masses of its constituent particlesWordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: penurious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language