Knuckle

1. The joint of a finger, particularly when made prominent by the closing of the fingers.
2. The kneejoint, or middle joint, of either leg of a quadruped, especially of a calf; -- formerly used of the kneejoint of a human being.
3. The joint of a plant.
4. (Mech.) The joining parts of a hinge through which the pin or rivet passes; a knuckle joint.
5. (Shipbuilding) 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.
6. 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; -- called also knuckle duster, knuckles or brass knuckles.
Knuckle joint (Mach.),
a hinge joint, in which a projection with an eye, on one piece, enters a jaw between two corresponding projections with eyes, on another piece, and is retained by a pin which passes through the eyes and forms the pivot.
Knuckle of veal (Cookery),
the lower part of a leg of veal, from the line of the body to the knuckle.

1. To submit to in a contest; to yield to.
2. To apply one's self vigorously or earnestly to; as, to knuckle to work.

1. To beat with the knuckles; to pummel.