knuckle

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. The prominence of the dorsal aspect of a joint of a finger, especially of one of the joints connecting the fingers to the hand.
2. n. A rounded protuberance formed by the bones in a joint.
3. n. A cut of meat centering on the carpal or tarsal joint, as of a pig.
4. n. The part of a hinge through which the pin passes.
5. n. A sharp angle formed by the meeting of two surfaces, especially two ship's timbers.
6. n. Brass knuckles.
7. v. To press, rub, or hit with the knuckles.
8. v. To shoot (a marble) with the thumb over the bent forefinger.
9. knuckle down To apply oneself earnestly to a task.
10. knuckle under To yield to pressure; give in.

Century Dictionary and Cyclopedia

1. n. The joint of a finger, especially that between the metacarpal bone and the first phalanx.
2. n. The knee or knee-joint.
3. n. A joint, especially of veal, consisting of the part of the leg called the knee. It is the part of the animal which corresponds to the hock of a horse, or the human heel, together with more or less of the leg above this joint.
4. n. The joint of a plant; a node.
5. n. A joint of cylindrical form, with a pin as axis, as that by which the straps of a hinge are fastened together.
6. n. In ship-building, an acute angle on some of the timbers.
7. n. plural Pieces of metal, usually brass (hence specifically known as brass knuckles), worn by lawless persons over the knuckles to protect them in striking a blow, and also to make a blow more effective. See knuckle-duster.
8. To touch or strike with the knuckle; pommel.
9. To bend the knuckles; hold the knuckles (that is, the hand) close to the ground, in playing marbles: usually with down. A player is required to knuckle down in order to keep him from gaining undue advantage by “hunching” nearer the mark.
10. To apply one's self earnestly, as to a task; engage vigorously, as in work.
11. To submit, as in a contest; give up; yield.
12. n. A sharply bent loop, as of intestine, especially when imprisoned, as in a hernia.
13. n. In mech., the swinging leaf or hook used for the coupling device in certain automatic car-couplings, particularly in the Janney or M. C. B. (master car-builders') type. A hole is usually provided in the knuckle so that the common link-coupling may be used with it.
14. To apply one's self earnestly.

Wiktionary

1. n. Any of the joints between the phalanges of the fingers.
2. n. by extension A mechanical joint.
3. n. A cut of meat.
4. n. sports, billiards, snooker, pool The curved part of the cushion at the entrance to the pockets on a cue sports table.
5. v. To apply pressure, or rub or massage with one's knuckles.

GNU Webster's 1913

1. n. The joint of a finger, particularly when made prominent by the closing of the fingers.
2. 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.
3. n. obsolete The joint of a plant.
4. n. (Mech.) The joining parts of a hinge through which the pin or rivet passes; a knuckle joint.
5. n. (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. n. Slang. 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.
7. v. To yield; to submit; -- used with down, to, or under.
8. v. rare To beat with the knuckles; to pummel.

WordNet 3.0

1. n. a joint of a finger when the fist is closed
2. v. press or rub with the knuckles
3. v. shoot a marble while keeping one's knuckles on the ground