The Collaborative International Dictionary of English v.0.48:

Gemsbok \Gems"bok\, n. [D.; akin to G. gemsbock the male or buck
   of the chamois; gemse chamois, goat of the Alps + bock buck.]
   (Zool.)
   A South African antelope (Oryx Capensis), having long,
   sharp, nearly straight horns.
   [1913 Webster]