/ Thesaurus / B Synonyms of bull mastiff Find synonyms for: Noun1. bull mastiff, working dogusage: large powerful breed developed by crossing the bulldog and the mastiffWordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: sequester Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language