[nuhk-uh l]


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

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

Verb Phrases

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.

Nearby words

  1. knt.,
  2. knub,
  3. knubbly,
  4. knubby,
  5. knuck,
  6. knuckle ball,
  7. knuckle down,
  8. knuckle joint,
  9. knuckle pads,
  10. knuckle sandwich

Origin of knuckle

1325–75; Middle English knokel (akin to Dutch kneukel, German Knöchel), diminutive of a word represented by Dutch knok, German Knochen bone; see -le

Related formsknuck·ly, adjective Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

British Dictionary definitions for knuckle down

knuckle down


(intr, adverb) informal to apply oneself diligentlyto knuckle down to some work



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


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

Derived Formsknuckly, adjective

Word Origin for knuckle

C14: related to Middle High German knöchel, Middle Low German knoke bone, Dutch knok

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for knuckle down



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).

Online Etymology Dictionary, © 2010 Douglas Harper

Medicine definitions for knuckle down




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.
A rounded protuberance formed by the bones in a joint.
A kink or loop of intestine, as in a hernia.

The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

Idioms and Phrases with knuckle down

knuckle down


Apply oneself seriously to some task or goal, as in The professor insisted that we knuckle down and get our papers in by Friday. Both this term and the rhyming synonym buckle down date from the 1860s, but the precise allusion in either is unclear.


See knuckle under.


In addition to the idioms beginning with knuckle

  • knuckle down
  • knuckle under

also see:

  • rap someone's knuckles
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.