hippopotamus

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A large, chiefly aquatic African herbivorous mammal (Hippopotamus amphibius) having thick, dark, almost hairless skin, short legs with four toes, and a broad, wide-mouthed muzzle. Also called river horse.
2. n. The pygmy hippopotamus.

Century Dictionary and Cyclopedia

1. n. An omnivorous ungulate pachydermatous mammal of the genus Hippopotamus or family Hippopotamidæ. The best-known species is the living African river-horse, H. amphibius. It has a thick and square head, a very large muzzle, small eyes and ears, thick and heavy body, short legs terminated by four toes, a short tail, two teats, skin about two inches thick on the back and sides, and no hair except at the extremity of the tail. The incisors and canines of the lower jaw are of great size and strength, the canines or tusks being long and curved forward. These tusks sometimes reach the length of two feet and more, and weigh upward of six pounds. It is chiefly on account of the tusks and teeth that the animal is killed, they being superior in hardness to ivory, and less liable to turn yellow. This hippopotamus inhabits nearly the whole of Africa; its flesh is eaten by the natives. It attains a length of about 14 feet, rarely more, and stands about 5 feet high. It delights in water, living in lakes, rivers, and estuaries, and feeding on water-plants, or on the herbage growing near the water. It is an excellent swimmer and diver, and can remain under water a considerable time. A much smaller and very different hippopotamus is Chœropsis liberiensis. See Chœropsinœ. There are several extinct species, of various genera.
2. n. [capitalized] [NL.] The typical genus of Hippopotamidæ, characterized by the presence of only four lower incisors. H. amphibius is the only living species.

Wiktionary

1. n. A large, semi-aquatic, herbivorous (plant-eating) African mammal (Hippopotamus amphibius) that spends most of the day living in water, but comes on to land at night to feed. Of all living land animals, only the rhinoceros and elephant are larger.

GNU Webster's 1913

1. n. (Zoöl.) A large, amphibious, herbivorous mammal (Hippopotamus amphibius), common in the rivers of tropical Africa. It is allied to the hogs, and has a very thick, naked skin, a thick and square head, a very large muzzle, small eyes and ears, thick and heavy body, and short legs. It is supposed to be the behemoth of the Bible. Called also zeekoe, and river horse. A smaller species (Hippopotamus Liberiencis) inhabits Western Africa.

WordNet 3.0

1. n. massive thick-skinned herbivorous animal living in or around rivers of tropical Africa