hitman vs gunslinger

hitman and gunslinger both are nouns.

Word	Noun	Adjective	Verb	Adverb
hitman	Yes	No	No	No
gunslinger	Yes	No	No	No

As nouns, hitman and gunslinger are synonyms defined as:

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

hitman (noun)	gunslinger (noun)
a professional killer who uses a gun	a professional killer who uses a gun