hippopotamuship‧po‧pot‧a‧mus /ˌhɪpəˈpɑt̮əməs/also hip‧po /ˈhɪpoʊ/ noun (plural hippopotamuses) [countable]Word Origin a large African animal with a big head, fat body, and thick gray skin, that lives in and near water [Origin: 1500–1600 Latin, Greek, from hippos “horse” + potamos “river”]