The Collaborative International Dictionary of English v.0.48:

Hyena \Hy*e"na\, n.; pl. Hyenas. [L. hyaena, Gr. ?, orig., a
   sow, but usually, a Libyan wild beast, prob., the hyena, fr.
   ? hog: cf. F. hy[`e]ne. See Sow female hog.] (Zool.)
   Any carnivorous mammal of the family Hy[ae]nid[ae], doglike
   nocturnal mammals of Africa and southern Asia, of which three
   living species are known. They are large and strong, but
   cowardly. They feed chiefly on carrion, and are nocturnal in
   their habits. [Written also hy[ae]na.]

   Syn: hyaena.
        [1913 Webster]

   Note: The striped hyena (Hy[ae]na striata) inhabits
         Southern Asia and a large part of Africa. The brown
         hyena (Hy[ae]na brunnea), and the spotted hyena
         (Crocuta maculata), are found in Southern Africa. The
         extinct cave hyena (Hy[ae]na spel[ae]a) inhabited
         England and France.
         [1913 Webster]

   Cave hyena. See under Cave.

   Hyena dog (Zool.), a South African canine animal (Lycaon
      venaticus), which hunts in packs, chiefly at night. It is
      smaller than the common wolf, with very large, erect ears,
      and a bushy tail. Its color is reddish or yellowish brown,
      blotched with black and white. Called also hunting dog.
      [1913 Webster]

WordNet (r) 3.0 (2006):

hyena dog
    n 1: a powerful doglike mammal of southern and eastern Africa
         that hunts in large packs; now rare in settled area [syn:
         African hunting dog, hyena dog, Cape hunting dog,
         Lycaon pictus]