The Collaborative International Dictionary of English v.0.48:

Hartbeest \Hart"beest`\, Hartebeest \Har"te*beest`\(-b[=e]st`),
   n. [D. hertebeest. See Hart, and Beast.]
   1. (Zool.) A large South African antelope (Alcelaphus
      caama), formerly much more abundant than it is now. The
      face and legs are marked with black, the rump with white.
      [Written also hartebeest, and hartebest.]
      [1913 Webster]

   2. Any anteleope of the genus Alcelaphus and certain
      species of Darnaliscus.
      [PJC]