Clio Syllabification: (Cli·o)Pronunciation: /ˈklīō, ˈklēō/Definition of Clio 1 Greek & Roman Mythology the Muse of history. 2an award given annually for advertising achievement in television, radio, billboards, and other media. Origin:from Greek kleiein 'celebrate'Clio in other Oxford dictionaries Definition of Clio in the British & World English dictionary