Synonyms for Hippo (same or very similar meaning)
WordNet sense 1 (an ancient Numidian town in northwestern Africa adjoining present-day Annaba in northeastern Algeria):
Hippo RegiusWordNet sense 2 (massive thick-skinned herbivorous animal living in or around rivers of tropical Africa):
hippopotamus, Hippopotamus amphibius, river horseFrom the ODE community, based on WordNetadd/edit