Panthera uncia vs big cat

Panthera uncia and big cat both are nouns.

Word	Noun	Adjective	Verb	Adverb
Panthera uncia	Yes	No	No	No
big cat	Yes	No	No	No

As nouns, big cat is a hypernym of Panthera uncia; that is, big cat is a word with a broader meaning than Panthera uncia:

Panthera uncia: large feline of upland central Asia having long thick whitish fur
big cat: any of several large cats typically able to roar and living in the wild

Other hypernyms of Panthera uncia include cat.

Panthera uncia (noun)	big cat (noun)
large feline of upland central Asia having long thick whitish fur	any of several large cats typically able to roar and living in the wild