knuckle

n. finger joint; rounded protuberance formed by the finger joint; cut of meat formed by the parts around the carpal or tarsal joint; part of the hinge into which the pin is inserted

v. press or rub with the knuckles; shoot a marble by flicking the thumb over the bent forefinger (in the game of marbles)

The knuckles are the joints of the fingers, which are brought into prominence when the hand is shut. The word is derived from the diminutive of a word for bone, found in German Knochen. Medically, it is said that the knuckles are formed by the metacarpophalangeal and interphalangeal joints of the finger. Knuckle-dusters or brass knuckles are said to have originally come from the criminal slang of the United States, and are brass or metal instrument fitting on to the hand across the knuckles, used to inflict a more brutal impact during a punch.
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Knuckle /knuck·le/ the dorsal aspect of any phalangeal joint, or any similarly bent structure. knuck·le n. 1. [more]Knuckle - Community and Resources

Noun
1. a joint of a finger when the fist is closed
(synonym) knuckle joint, metacarpophalangeal joint
(hypernym) synovial joint, articulatio synovialis, diarthrosis
(part-holonym) finger
Verb
1. press or rub with the knuckles
(hypernym) press
(derivation) knuckle joint, metacarpophalangeal joint
2. shoot a marble while keeping one's knuckles on the ground
(hypernym) shoot

(v. t.)
To beat with the knuckles; to pommel.
  

(v. i.)
To yield; to submit; -- used with down, to, or under.
  

(n.)
The kneejoint, or middle joint, of either leg of a quadruped, especially of a calf; -- formerly used of the kneejoint of a human being.
  

(n.)
The joint of a plant.
  

(n.)
The joint of a finger, particularly when made prominent by the closing of the fingers.
  

(n.)
The joining pars of a hinge through which the pin or rivet passes; a knuckle joint.
  

(n.)
A convex portion of a vessel's figure where a sudden change of shape occurs, as in a canal boat, where a nearly vertical side joins a nearly flat bottom.
  

(n.)
A contrivance, usually of brass or iron, and furnished with points, worn to protect the hand, to add force to a blow, and to disfigure the person struck; as, brass knuckles; -- called also knuckle duster.