ninepin vs bowling pin

ninepin and bowling pin both are nouns.

Word	Noun	Adjective	Verb	Adverb
ninepin	Yes	No	No	No
bowling pin	Yes	No	No	No

As nouns, bowling pin is a hypernym of ninepin; that is, bowling pin is a word with a broader meaning than ninepin:

ninepin: a bowling pin of the type used in playing ninepins or (in England) skittles
bowling pin: a club-shaped wooden object used in bowling; set up in triangular groups of ten as the target

Other hypernyms of ninepin include pin.

ninepin (noun)	bowling pin (noun)
a bowling pin of the type used in playing ninepins or (in England) skittles	a club-shaped wooden object used in bowling; set up in triangular groups of ten as the target