mountain lion vs panther

mountain lion and panther both are nouns.

Word	Noun	Adjective	Verb	Adverb
mountain lion	Yes	No	No	No
panther	Yes	No	No	No

As nouns, mountain lion and panther are synonyms defined as:

Other synonyms of mountain lion include catamount, cougar, Felis concolor, painter, puma.

mountain lion (noun)	panther (noun)
large American feline resembling a lion	a leopard in the black color phase
	a large spotted feline of tropical America similar to the leopard; in some classifications considered a member of the genus Felis
	large American feline resembling a lion