/ Thesaurus / O Synonyms of open letter Find synonyms for: Noun1. open letter, letter, missiveusage: a letter of protest; addressed to one person but intended for the general publicWordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: diligent Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language