cheerfulness n. + Add to list US //ˈtʃɪɹfəɫnəs// UK //tʃˈiəfəlnəs// cheer·ful·ness SynonymsAntonymsEtymology Synonyms blithenesscheersunninesssunshine Antonyms cheerlessnessuncheerfulnessOriginMEcherefulnes→ENcheerfulness From Middle English cherefulnes; equivalent to cheerful + -ness.