knucklebone Syllabification: (knuck·le·bone)Pronunciation: /ˈnəkəlˌbōn/Definition of knucklebone noun 1a bone forming or corresponding to a knuckle. a knuckle of meat. 2 (knucklebones) animal knucklebones used in the game of jacks. the game of jacks. knucklebone in other Oxford dictionaries Definition of knucklebone in the British & World English dictionary