knuckle
n. countablen. one of the hard, bony parts of your hand where your fingers bend. You can see them clearly when you make a fist.
n. a joint of a finger, especially one of the articulations between a metacarpal bone and a phalanx. Often used in the plural when referring to the physical impact of a punch.
He scraped his knuckle while fixing the car.
She rapped her knuckles against the wooden door to see if anyone was home.
The boxer's knuckles were heavily taped to prevent fractures during the high-impact rounds of the championship match.
From Middle English knokel (“finger joint”), from Old English cnucel (“the juncture of two bones; knuckle; joint”), from Proto-West Germanic knukil, from Proto-Germanic knukilaz (“knuckle, knot, bump”), as knukô (“bone, joint”) + -ilaz (diminutive suffix). Cognate with Dutch knokkel (“knuckle”), Low German Knökel (“knuckle”), German Knöchel (“ankle, knuckle”), Old Norse knykill.
Commonly used in the plural; often appears in idioms like 'a rap on the knuckles' or 'white-knuckle'.