cabby vs hack driver

cabby and hack driver both are nouns.

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

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

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

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