/ Thesaurus / B Synonyms of box girder Find synonyms for: Noun1. box beam, box girder, beamusage: a beam built up from boards; has a hollow rectangular cross sectionWordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: devout Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language