/ Thesaurus / - Synonyms of ious Find synonyms for: Noun1. IOU, note, promissory note, note of handusage: an informal debt instrument; representing `I owe you'WordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: secular Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language