punching ball vs punchball

punching ball and punchball both are nouns.

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

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

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

Other synonyms of punching ball include punch bag, punching bag.

punching ball (noun)	punchball (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