to do something prematurely
I think I jumped the gun on calling her "bitch." she won't talk to me anymore, I guess it was too early.
to do something too soon
, especially without thinking carefully about it (Originally used in sports contests that are started by firing a gun
. If someone running in a race jumps the gun, they start running before the gun has been fired to start the race.)
He shouted at me before I had time to explain, but later he apologised for jumping the gun (jump the gun).
To commit suicide, not necessarily by use of a gun.
Bob Jumped the gun because his wife was cheating on him.