The Collaborative International Dictionary of English v.0.48:
Sassaby \Sas"sa*by\, Sassabye \Sas"sa*bye\, n. (Zool.) A large African antelope (Alcelaphus lunata), similar to the hartbeest, but having its horns regularly curved. [1913 Webster]WordNet (r) 3.0 (2006):
sassaby n 1: a large South African antelope; considered the swiftest hoofed mammal [syn: sassaby, topi, Damaliscus lunatus]