Meaning of punching bag

punch'ing bag"

Pronunciation: [key]
  1. an inflated or stuffed bag, usually suspended, punched with the fists as an exercise.
  2. a person serving as an object of abuse; scapegoat: I told him that I wasn't going to be a punching bag for anyone.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.