v. i. [ imp. & p. p. Knuckled ; p. pr. & vb. n. Knuckling ] To yield; to submit; -- used with down, to, or under. [ 1913 Webster ]

To knuckle to. (a) To submit to in a contest; to yield to. [ Colloq. ] See To knock under, under Knock, v. i. (b) To apply one's self vigorously or earnestly to; as, to knuckle to work. [ Colloq. ] [ 1913 Webster ]

v. t. To beat with the knuckles; to pummel. [ R. ] Horace Smith. [ 1913 Webster ]

n. [ OE. knokel, knokil, AS. cuncel; akin to D. knokkel, OFries. knokele, knokle, G. knöchel, Sw. knoge, Dan. knokkel, G. knochen bone, and perh. to E. knock. ] 1. The joint of a finger, particularly when made prominent by the closing of the fingers. Davenant. [ 1913 Webster ]

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. [ 1913 Webster ]

With weary knuckles on thy brim she kneeled sadly down. Golding. [ 1913 Webster ]

3. The joint of a plant. [ Obs. ] Bacon. [ 1913 Webster ]

4. (Mech.) The joining parts of a hinge through which the pin or rivet passes; a knuckle joint. [ 1913 Webster ]

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. [ 1913 Webster ]

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. ] [ 1913 Webster ]

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. [ 1913 Webster ]

a. Jointed. [ Obs. ] Bacon. [ 1913 Webster ]

n. pl. a small metal weapon, worn over the knuckles on the back of the hand; called also brass knuckles and knuckle duster.
Syn. -- brass knucks, knucks, brass knuckles, knuckle duster. [ WordNet 1.5 ]

v. i. To yield; to submit; -- usually used with to. [ PJC ]