racer vs automobile driver

racer and automobile driver both are nouns.

Word	Noun	Adjective	Verb	Adverb
racer	Yes	No	No	No
automobile driver	Yes	No	No	No

As nouns, racer and automobile driver are synonyms defined as:

racer and automobile driver: someone who drives racing cars at high speeds

Other synonyms of racer include race driver.

racer (noun)	automobile driver (noun)
an animal that races	someone who drives racing cars at high speeds
slender fast-moving North American snakes
a fast car that competes in races
someone who drives racing cars at high speeds