Noun
A bone that forms a knuckle in the human hand, in an animal's paw or any bone that forms a similar bump.
Such a bone once used in knucklebones and other children's games of chance.
(slang) A die.
Source: en.wiktionary.orgAnd what of the dead? They lie without shoes in their stone boats. They are more like stone than the sea would be if it stopped. They refuse to be blessed, throat, eye and knucklebone. Anne Sexton