/ Thesaurus / O Synonyms of onion mildew Find synonyms for: Noun1. onion mildew, Peronospora destructor, downy mildew, false mildewusage: fungus causing a downy mildew on onionsWordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: rustic Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language