Source : Webster's Revised Unabridged Dictionary (1913)

Sassaby \Sas"sa*by\, Sassabye \Sas"sa*bye\, n. (Zo["o]l.)
   A large African antelope ({Alcelaphus lunata}), similar to
   the hartbeest, but having its horns regularly curved.

Source : WordNet®

sassaby
     n : a large South African antelope; considered the swiftest
         hoofed mammal [syn: {topi}, {Damaliscus lunatus}]