Rock Cornish vs domestic fowl

Rock Cornish and domestic fowl both are nouns.

Word	Noun	Adjective	Verb	Adverb
Rock Cornish	Yes	No	No	No
domestic fowl	Yes	No	No	No

As nouns, domestic fowl is a hypernym of Rock Cornish; that is, domestic fowl is a word with a broader meaning than Rock Cornish:

Rock Cornish: small plump hybrid developed by crossbreeding Plymouth Rock and Cornish fowl
domestic fowl: a domesticated gallinaceous bird thought to be descended from the red jungle fowl

Other hypernyms of Rock Cornish include fowl, poultry.

Rock Cornish (noun)	domestic fowl (noun)
small plump hybrid developed by crossbreeding Plymouth Rock and Cornish fowl	a domesticated gallinaceous bird thought to be descended from the red jungle fowl