blacksnake vs black rat snake

blacksnake and black rat snake both are nouns.

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

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

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

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

blacksnake (noun)	black rat snake (noun)
blackish racer of the eastern United States that grows to six feet	large harmless shiny black North American snake
large harmless shiny black North American snake