Breadcrumb Home > Thesaurus > W Synonyms of welsh onion Find synonyms for: Noun1. Welsh onion, Japanese leek, Allium fistulosum, onion, onion plant, Allium cepausage: Asiatic onion with slender bulbs; used as early green onionsWordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. ✖ Related Content Daily Word Quiz: sepulture Analogy of the Day: Today’s Analogy Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language