B1 a weapon that bullets or shells (= explosive containers) are fired from:
The British police do not carry guns.
You could hear the noise of guns firing in the distance.
in sport, a device that makes a very loud sudden noise as a signal to start a race:
At the gun, the runners sprinted away down the track.
a device that you hold in your hand and use for sending out a liquid or object:
a spray gun
hired gun mainly US informal a person who is paid to shoot and kill someone