punching ball vs punching bag

punching ball and punching bag both are nouns.

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

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

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

Other synonyms of punching ball include punch bag, punchball.

punching ball (noun)	punching bag (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
	a person on whom another person vents their anger