Noun

1. A weapon that discharges a missile at high velocity (especially from a metal tube or barrel)
2. Large but transportable armament
3. A person who shoots a gun (as regards their ability)
4. A professional killer who uses a gun
5. A hand-operated pump that resembles a revolver; forces grease into parts of a machine
6. A pedal that controls the throttle valve
7. The discharge of a firearm as signal or as a salute in military ceremonies

Verb

1. Shoot with a gun