gazelle hound vs hound dog

gazelle hound and hound dog both are nouns.

Word	Noun	Adjective	Verb	Adverb
gazelle hound	Yes	No	No	No
hound dog	Yes	No	No	No

As nouns, hound dog is a hypernym of gazelle hound; that is, hound dog is a word with a broader meaning than gazelle hound:

gazelle hound: old breed of tall swift keen-eyed hunting dogs resembling greyhounds; from Egypt and southwestern Asia
hound dog: any of several breeds of dog used for hunting typically having large drooping ears

Other hypernyms of gazelle hound include hound.

gazelle hound (noun)	hound dog (noun)
old breed of tall swift keen-eyed hunting dogs resembling greyhounds; from Egypt and southwestern Asia	any of several breeds of dog used for hunting typically having large drooping ears