a rap on/over/across the knuckles
 a rap on/over/across the knuckles — see rap, 1
 • • •
 Main Entry: knuckle
————————
 a rap on/over/across the knuckles
   informal   : criticism or punishment that is given in a gentle way for something that you did wrong
   I received a rap on the knuckles for missing the meeting.
 • • •
 Main Entry: rap