/ Dictionary / Index B box beam: Meaning and Definition of Find definitions for: box' beam" Pronunciation: [key] a beam or girder built up from shapes and having a hollow, rectangular cross section. Also called Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. boxball box bed Related Content Daily Word Quiz: paradox Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language