A punching bag is read as a safe outlet for anger and frustration. Hitting one reflects tension seeking release; being one, the sense of absorbing everyone else’s blows.
When this appeared in your dream, what were you feeling?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.