To jump the gun is to start before it is time. Do not jump the gun.
It comes from sprinting, where the runner moves before the starting pistol fires. To jump the gun on an announcement is the commonest way of ruining one.
1phrasejump the gunTo start before it is time.
“They jump the gun every year and put the decorations up in November.”
jump the gun is a phrase.
Practised in Idioms