knuckle under


  1. a joint of a finger, especially one of the articulations of a metacarpal with a phalanx.
  2. the rounded prominence of such a joint when the finger is bent.
  3. a joint of meat, consisting of the parts about the carpal or tarsal joint of a quadruped.
  4. an angle or protrusion at the intersection of two members or surfaces, as in the timbers of a ship or in a roof.
  5. brass knuckles.
  6. a cylindrical projecting part on a hinge, through which an axis or pin passes; the joint of a hinge.
  7. (in a wire mesh) a bend in a wire crossing another wire.
  8. (on a chair arm) one of the ridges left at the front end by longitudinal flutes carved to accommodate the fingers.
  9. Nautical. a pronounced edge formed by a change in the form of the shell of a hull.

verb (used with object), knuck·led, knuck·ling.

  1. to rub or press with the knuckles.
  2. Marbles. to shoot (a marble) from the thumb and forefinger.

Verb Phrases

  1. knuckle down,
    1. to apply oneself vigorously and earnestly; become serious: Just knuckle down for an hour or so and finish the work.
    2. Also knuckle submit; yield.


  1. (intr, adverb) to give way under pressure or authority; yield


  1. a joint of a finger, esp that connecting a finger to the hand
  2. a joint of veal, pork, etc, consisting of the part of the leg below the knee joint, often used in making stews or stock
  3. the cylindrical portion of a hinge through which the pin passes
  4. an angle joint between two members of a structure
  5. near the knuckle informal approaching indecency


  1. (tr) to rub or press with the knuckles
  2. (intr) to keep the knuckles on the ground while shooting a marble

mid-14c., knokel “finger joint; any joint of the body, especially a knobby one; morbid lump or swelling;” common Germanic (cf. Middle Low German knökel, Middle Dutch cnockel, German knöchel), literally “little bone,” a diminutive of Proto-Germanic root *knuck- “bone” (cf. German Knochen “bone).

As a verb from 1740, originally in the game of marbles. To knuckle down “apply oneself earnestly” is 1864 in American English, extended from marbles (putting a knuckle on the ground in assuming the hand position preliminary to shooting); to knuckle under “submit, give in” is first recorded 1740, supposedly from the former more general sense of “knuckle” and here meaning “knee,” hence “to kneel.” The face-busting knuckle-duster is from 1858 (a duster was a type of protective coat worn by workmen).


  1. The prominence of the dorsal aspect of a joint of a finger, especially of one of the joints that connect the fingers to the hand.
  2. A rounded protuberance formed by the bones in a joint.
  3. A kink or loop of intestine, as in a hernia.

Also, knuckle down. Give in, acknowledge defeat, as in The dean refused to knuckle under to the graduate students’ demands, or He was forced to knuckle down before their threats of violence. Presumably this idiom alludes to a kneeling position with hands on the ground, knuckles down. [Mid-1700s]

In addition to the idioms beginning with knuckle

  • knuckle down
  • knuckle under

also see:

  • rap someone’s knuckles

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