/ Thesaurus / I Synonyms of illinois river Find synonyms for: Noun1. Illinois Riverusage: a river in Illinois that flows southwest to the Mississippi RiverWordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: acquiesce Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language