prowl car vs auto

prowl car and auto both are nouns.

Word	Noun	Adjective	Verb	Adverb
prowl car	Yes	No	No	No
auto	Yes	No	No	No

As nouns, auto is a hypernym of prowl car; that is, auto is a word with a broader meaning than prowl car:

prowl car: a car in which policemen cruise the streets; equipped with radiotelephonic communications to headquarters
auto: a motor vehicle with four wheels; usually propelled by an internal combustion engine

Other hypernyms of prowl car include automobile, car, machine, motorcar.

prowl car (noun)	auto (noun)
a car in which policemen cruise the streets; equipped with radiotelephonic communications to headquarters	a motor vehicle with four wheels; usually propelled by an internal combustion engine