/ Thesaurus / M Synonyms of mellow out Find synonyms for: Verb1. mellow, melt, mellow out, changeusage: become more relaxed, easygoing, or genial; "With age, he mellowed"WordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: effervescent Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language