A gun is a weapon from which bullets or other things are fired.

A gun or a starting gun is an object like a gun that is used to make a noise to signal the start of a race.

To gun an engine or a vehicle means to make it start or go faster by pressing on the accelerator pedal.

If you come out with guns blazing or with all guns blazing, you put all your effort and energy into trying to achieve something.

If you jump the gun, you do something before everyone else or before the proper or right time.

If you stick to your guns, you continue to have your own opinion about something even though other people are trying to tell you that you are wrong.