: a very large herbivorous 4-toed chiefly aquatic artiodactyl mammal (Hippopotamus amphibius) of sub-Saharan Africa with an extremely large head and mouth, bare and very thick grayish skin, and short legs; also: a smaller closely related mammal (Choeropsis liberiensis) of western Africa
: a large African animal with thick hairless brownish gray skin, a big head, and short legs that eats plants and spends most of its time in rivers
Word History of HIPPOPOTAMUS
The bulky African mammal that spends its daytime hours sunk up to its eyes in a river owes its English name to the ancient Greeks. The historian Herodotus called the animal, which he may have seen in Egypt, ho hippos ho potamios, “the river horse.” Later Greek writers reduced this description to hippopotamos (which looks as if it should mean “horse river”). Despite its name, the hippopotamus is more closely related to hogs than horses.