The DICT Development Group

  Hippopotamus \Hip`po*pot"a*mus\, n.; pl. E. Hippopotamuses, L.
     Hippopotami. [L., from Gr.?; "i`ppos horse + ? river. Cf.
     Equine.] (Zool.)
     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.
     [1913 Webster]

  pachyderm \pach"y*derm\ (p[a^]k"[i^]*d[~e]rm), n. [Cf. F.
     pachyderme.] (Zool.)
     Any of various nonruminant hoofed mammals having very thick
     skin, including the elephant, rhinoceros, and
     hippopotamus, one of the Pachydermata.
     [WordNet 1.5 + 1913 Webster]

  hippopotamus
      n 1: massive thick-skinned herbivorous animal living in or
           around rivers of tropical Africa [syn: hippopotamus,
           hippo, river horse, Hippopotamus amphibius]