1. (noun)
knuckle, knuckle joint, metacarpophalangeal joint
- a joint of a finger when the fist is closed Synonyms: metacarpophalangeal joint, knucklejoint, hingejoint, knuckle
2. (verb)
knuckle
- press or rub with the knuckles
3. (verb)
knuckle
- shoot a marble while keeping one's knuckles on the ground