The Collaborative International Dictionary of English v.0.48:

Grysbok \Grys"bok\n. [D. grijs gray + bok buck.] (Zool.)
   A small South African antelope (Neotragus melanotis). It is
   speckled with gray and chestnut, above; the under parts are
   reddish fawn.
   [1913 Webster]