What is Knuckle?

Knuckle definition and meaning on Dictionary terms:
a joint of a finger, especially one of the articulations of a metacarpal with a phalanx.
the rounded prominence of such a joint when the finger is bent.
a joint of meat, consisting of the parts about the carpal or tarsal joint of a quadruped.

an angle or protrusion at the intersection of two members or surfaces, as in the timbers of a ship or in a roof.
brass knuckles.
a cylindrical projecting part on a hinge, through which an axis or pin passes; the joint of a hinge.
(in a wire mesh) a bend in a wire crossing another wire.
(on a chair arm) one of the ridges left at the front end by longitudinal flutes carved to accommodate the fingers.
Nautical. a pronounced edge formed by a change in the form of the shell of a hull.

verb (used with object), knuck