Knuckle

1. 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.
2. n. The joint of a finger, particularly when made prominent by the closing of the fingers.
3. 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.
4. n. The joint of a plant.
5. n. The joining pars of a hinge through which the pin or rivet passes; a knuckle joint.
6. 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.

The word meanings were obtained from OPTED(The Online Plain Text English Dictionary), which is based on “The Project Gutenberg Etext of Webster’s Unabridged Dictionary” which is in turn based on the 1913 US Webster’s Unabridged Dictionary (See Project Gutenburg), as a text file.