/ Thesaurus / S Synonyms of secondary diagonal Find synonyms for: Noun1. secondary diagonal, diagonalusage: the diagonal of a square matrix running from the lower left entry to the upper right entryWordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: illegible Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language