Breadcrumb Home > Thesaurus > P Synonyms of perniciousness Find synonyms for: Noun1. perniciousness, toxicity, unwholesomeness, morbidness, morbidityusage: grave harmfulness or deadlinessWordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. ✖ Related Content Daily Word Quiz: perambulate Analogy of the Day: Today’s Analogy Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language