Definition of knuckle

• n. - The joint of a finger, particularly when made prominent by the closing of the fingers.
• 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 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.
• v. i. - To yield; to submit; -- used with down, to, or under.
• v. t. - To beat with the knuckles; to pommel.