hack driver vs hack-driver

hack driver and hack-driver both are nouns.

Word	Noun	Adjective	Verb	Adverb
hack driver	Yes	No	No	No
hack-driver	Yes	No	No	No

As nouns, hack driver and hack-driver are synonyms defined as:

Other synonyms of hack driver include cabby, cabdriver, cabman, livery driver, taxidriver, taximan.

hack driver (noun)	hack-driver (noun)
someone who drives a taxi for a living	someone who drives a taxi for a living