To let off

To discharge; to let fly, as an arrow; to fire the charge of, as a gun.
To release, as from an engagement or obligation.

See also: Let, Let

Webster's Revised Unabridged Dictionary, published 1913 by G. & C. Merriam Co.
References in classic literature ?
Who is it, I said, whom you are refusing to let off?
The chec and his attendants, though I had given them notice that we were going to let off our guns in honour of the King their master, could not forbear trembling at the fire and noise.
For a moment, the whole party stood in suspense, awaiting the result, and then a simultaneous impulse caused the whole to let off their pieces at the same instant, producing a noise which might not fail to reach the ears of all within so short a distance.
Her brother Petya was upstairs too; with the man in attendance on him he was preparing fireworks to let off that night.
"Why--he was standing over the whey-tub to let off the whey, and the shade of his face came upon the wall behind, close to Izz, who was standing there filling a vat.
It was an unthoughtful act in a man who has so often slept with the war-whoop ringing in the air, to let off his piece within sound of an ambushment!
It is also illegal to let off or throw fireworks (including sparklers) in the street or other public places.
PART of the money from fines that will be collected when traffic cameras are finally installed next year, will go to creating racing tracks for young drivers to let off steam, police said yesterday.
"Castle Hill's presence in the local landscape makes it a popular venue to let off fireworks.
READY TO LET OFF STEAM Harry and Grace Courtney at Chesters Roman Fort in Hexham, one of the sites where events will be held
Either way, if men are driving you mad and you need to let off some steam, book that place on the couch and let Thelma and Louise remind you why we are the superior sex.
Northern Ireland star Clarke, 40, was so annoyed after a 78 in his third round he went to the pub to let off steam.