cheerio n. + Add to list US //ˈtʃɪɹioʊ// UK //tʃˈiəɹɪˌəʊ// chee·rio Archaic Informal SynonymsEtymology Synonyms adieuadiosarrivedercibyebye byegood bygood byegoodbyOrigin From cheer and/or cheery + -o.