The Collaborative International Dictionary of English v.0.48:

Oryx \O"ryx\ ([=o]"r[i^]ks), prop. n. [NL., from Gr. 'o`ryx a
   kind of gazelle or antelope.] (Zool.)
   A genus of African antelopes which includes the gemsbok, the
   leucoryx, the bisa antelope (Oryx beisa), and the beatrix
   antelope (Oryx beatrix) of Arabia.
   [1913 Webster]

WordNet (r) 3.0 (2006):

oryx
    n 1: large African antelope with long straight nearly upright
         horns [syn: oryx, pasang]