Short for rhinocerus, a native of the African savanna. There are two types, the black rhino which is the smallest but more agressive beast and the white rhino which has a square lip; and although larger than the black rhino is much more docile.
Both animals have a double "horn" on the front of their heads,. Not really horn at all but compressed hair and in big demand, thought to be an aphrodisiac, especially by people in the far east......
Oh shut up Clay, I've just noticed, Gary is talking about a fishing rod.