hired gun vs gun

hired gun and gun both are nouns.

Word	Noun	Adjective	Verb	Adverb
hired gun	Yes	No	No	No
gun	Yes	No	Yes	No

As nouns, hired gun and gun are synonyms defined as:

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

hired gun (noun)	gun (noun)
a professional killer who uses a gun	the discharge of a firearm as signal or as a salute in military ceremonies
	a weapon that discharges a missile at high velocity (especially from a metal tube or barrel)
	large but transportable armament
	a hand-operated pump that resembles a pistol; forces grease into parts of a machine
	a pedal that controls the throttle valve
	a professional killer who uses a gun
	a person who shoots a gun (as regards their ability)

hired gun (verb)	gun (verb)
	shoot with a gun