Water buck \Wa"ter buck`\ (Zo["o]l.) A large, heavy antelope ({Kobus ellipsiprymnus}) native of Central Africa. It frequents the banks of rivers and is a good swimmer. It has a white ring around the rump. Called also {photomok}, {water antelope}, and {waterbok}. Note: The name is also applied to other related species, as the leche ({Kobus leche}), which has similar habits.