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. "With weary knuckles on thy brim she kneeled sadly down."
3.The joint of a plant. (Obs.)
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. (Slang.)