Nouns

(n)guna weapon that discharges a missile at high velocity (especially from a metal tube or barrel)
(n)artillery, heavy weapon, gun, ordnancelarge but transportable armament
(n)gun, gunnera person who shoots a gun (as regards their ability)
(n)gunslinger, hired gun, gun, gun for hire, triggerman, torpedo, shootera professional killer who uses a gun
(n)grease gun, guna hand-operated pump that resembles a pistol; forces grease into parts of a machine
(n)accelerator, accelerator pedal, gas pedal, gas, throttle, guna pedal that controls the throttle valve“he stepped on the gas”
(n)gunthe discharge of a firearm as signal or as a salute in military ceremonies“two runners started before the gun”, “a twenty gun salute”

Verbs

(v)gunshoot with a gun