Meaning of rap someone's knuckles | Babel Free

Definitions

1. to tap one's knuckles on an object such as a desk or wall to attract attention or as a signal of commmunication.
   literally
2. to give someone a punishment.
   dated, idiomatic
3. to strike someone on the back of the hand usually as a method of punishment.
   archaic, literally

Examples

“Just rap your knuckles on the wall when you're ready to go.”

“The professor let this go for a moment, then began to rap his knuckles on the podium until the room quieted again.”

“If the sales department doesn't get organized soon, the CEO is going to rap their knuckles.”

“... while political science at Western had received a sharp rap across its knuckles.”

“In the old days the teacher would rap someone's knuckles with a ruler if they misbehaved in class.”

“...she commanded, sounding for all the world like a mean old schoolmarm about to rap his knuckles with her ruler.”

CEFR level