gun vs gun for hire

gun and gun for hire both are nouns.

Word	Noun	Adjective	Verb	Adverb
gun	Yes	No	Yes	No
gun for hire	Yes	No	No	No

As nouns, gun and gun for hire are synonyms defined as:

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

gun (noun)	gun for hire (noun)
the discharge of a firearm as signal or as a salute in military ceremonies	a professional killer who uses a gun
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)

gun (verb)	gun for hire (verb)
shoot with a gun