Breadcrumb Home > Thesaurus > C Synonyms of cio Find synonyms for: Noun1. Congress of Industrial Organizations, CIO, federationusage: a federation of North American industrial unions that merged with the American Federation of Labor in 1955WordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved.Definition and meaning of cio (Dictionary) ✖ Related Content Daily Word Quiz: prandial Analogy of the Day: Today’s Analogy Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language