58-jumping the gun

Dear all

Hello

What does it mean when they say:

He is Jumping his gun.

Thanks a million

Matilda

Jumping the gun means to act prematurely.

The most common way I have heard that phrase used is:
He/she is jumping the gun.
You’re jumping the gun.
Don’t jump the gun.

Example usage:

Bob won the race against Tim because Bob jumped the gun.