cheerio/ˈtʃɪrioʊ/1an informal way of saying goodbye or farewellI'll see you tomorrow, cheerio!Cheerio, old chap!Have a splendid day.Cheerio, my dear friend.Until we meet again.Synonyms: adiosadieugoodbysayonarabyeso longarrivederciau revoirbye-byegood-bygood daygoodbyeauf wiedersehengood-bye