gunslinger vs hit man

gunslinger and hit man both are nouns.

Word	Noun	Adjective	Verb	Adverb
gunslinger	Yes	No	No	No
hit man	Yes	No	No	No

As nouns, gunslinger and hit man are synonyms defined as:

Other synonyms of gunslinger include gun, gun for hire, gunman, hired gun, hitman, shooter, torpedo, triggerman.

gunslinger (noun)	hit man (noun)
a professional killer who uses a gun	a professional killer who uses a gun