punchball vs punching bag

punchball and punching bag both are nouns.

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

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

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

Other synonyms of punchball include punch bag, punching ball.

punchball (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