racer vs blacksnake

racer and blacksnake both are nouns.

Word	Noun	Adjective	Verb	Adverb
racer	Yes	No	No	No
blacksnake	Yes	No	No	No

As nouns, blacksnake is a hyponym of racer; that is, blacksnake is a word with a more specific, narrower meaning than racer:

racer: slender fast-moving North American snakes
blacksnake: blackish racer of the eastern United States that grows to six feet

racer (noun)	blacksnake (noun)
an animal that races	blackish racer of the eastern United States that grows to six feet
slender fast-moving North American snakes	large harmless shiny black North American snake
a fast car that competes in races
someone who drives racing cars at high speeds