/ Thesaurus / B Synonyms of billet doux Find synonyms for: Noun1. love letter, billet doux, personal letterusage: a personal letter to a loved one expressing affectionWordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: aversion Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language