The Collaborative International Dictionary of English v.0.48:

okapi \o*ka"pi\, n. [Native name on the borders of Belgian
   Congo, possibly the same word as Mpongwe okapo lean.]
   A peculiar mammal (Okapia johnstoni) closely related to the
   giraffe, discovered in the deep forests of Belgian Congo in
   1900. It is smaller than an ox, and somewhat like a giraffe,
   except that the neck is much shorter. Like the giraffe, it
   has no dewclaws. There is a small prominence on each frontal
   bone of the male. The color of the body is chiefly reddish
   chestnut, the cheeks are yellowish white, and the fore and
   hind legs above the knees and the haunches are striped with
   purplish black and cream color.
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

okapi
    n 1: similar to the giraffe but smaller with much shorter neck
         and stripe on the legs [syn: okapi, Okapia johnstoni]