/ Thesaurus / A Synonyms of atomic number 5 Find synonyms for: Noun1. boron, B, atomic number 5, chemical element, elementusage: a trivalent metalloid element; occurs both in a hard black crystal and in the form of a yellow or brown powderWordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: kiln Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language