/ Thesaurus / L Synonyms of letters patent Find synonyms for: Noun1. patent, letters patent, legal document, legal instrument, official document, instrumentusage: an official document granting a right or privilegeWordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: grimace Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language