/ Thesaurus / F Synonyms of flatten out Find synonyms for: Verb1. flatten, flatten out, change shape, change form, deformusage: become flat or flatter; "The landscape flattened"WordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: panacea Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language