slam on the brakes

slam on the brakes (third-person singular simple present slams on the brakes, present participle slamming on the brakes, simple past and past participle slammed on the brakes)

1. (idiomatic, transitive) To press down hard on the brakes of a vehicle in order to make it stop suddenly.
   • 1944 July and August, “Top Link Drivers: XXI—Driver H. Blunt, L.N.E.R.”, in Railway Magazine, page 226:

     Driving 2-6-2 locomotive No. 4771 Green Arrow, Blunt suddenly noticed that the tunnel mouth was silhouetted in a dazzling white glare and that incendiary bombs were showering down in their hundreds, he slammed on all his brakes and brought his train to a stop just inside the tunnel.

• jam on the brakes