- any one of the thick, bony parts (called joints) in your fingers
- She rapped her knuckles on the table.
- a pork knuckle
- It's time to knuckle down and get to work.
- She knuckled down to the task.
- to stop trying to fight or resist something
- Despite the pressure, he refused to knuckle under. [=give in]
- He refused to knuckle under to anyone.
- He finally knuckled under to the pressure.