cabman vs hack driver

cabman and hack driver both are nouns.

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

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

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

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