Noun
a bone that is given to a dog to chew on and play with, similar to a dog biscuit. They can be real bones, or they can be made of other materials like plastic or leather
a 2- or 3-dimensional compound shape, evocative of a dog biscuit or dog-bone toy with a central shaft and two lobes (analogous to femoral condyles) at each end
(slang, possibly African-American Vernacular) the penis
Source: en.wiktionary.org