basset hound vs hound dog

basset hound and hound dog both are nouns.

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

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

basset hound: smooth-haired breed of hound with short legs and long ears
hound dog: any of several breeds of dog used for hunting typically having large drooping ears

Other hypernyms of basset hound include hound.

basset hound (noun)	hound dog (noun)
smooth-haired breed of hound with short legs and long ears	any of several breeds of dog used for hunting typically having large drooping ears