mountain blacksnake vs black rat snake

mountain blacksnake and black rat snake both are nouns.

Word	Noun	Adjective	Verb	Adverb
mountain blacksnake	Yes	No	No	No
black rat snake	Yes	No	No	No

As nouns, mountain blacksnake and black rat snake are synonyms defined as:

mountain blacksnake and black rat snake: large harmless shiny black North American snake

Other synonyms of mountain blacksnake include blacksnake, Elaphe obsoleta, pilot blacksnake.

mountain blacksnake (noun)	black rat snake (noun)
large harmless shiny black North American snake	large harmless shiny black North American snake