hit man vs hitman

hit man and hitman both are nouns.

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

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

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

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