punch bag vs punching ball

punch bag and punching ball both are nouns.

Word	Noun	Adjective	Verb	Adverb
punch bag	Yes	No	No	No
punching ball	Yes	No	No	No

As nouns, punch bag and punching ball are synonyms defined as:

punch bag and punching ball: an inflated ball or bag that is suspended and punched for training in boxing

Other synonyms of punch bag include punchball, punching bag.

punch bag (noun)	punching ball (noun)
an inflated ball or bag that is suspended and punched for training in boxing	an inflated ball or bag that is suspended and punched for training in boxing