jam on
phrasal verb.phrasal verb. to press something down quickly and with a lot of force, usually the brakes of a car.
phrasal verb. to apply something—typically vehicle brakes—suddenly and forcefully; often used to describe an emergency or reflexive action.
I had to jam on the brakes when the cat ran out.
The driver ahead of me jammed on his brakes for no reason, nearly causing a pile-up.
As the train approached the blocked crossing, the engineer jammed on the emergency brakes, sending a screeching sound through the valley.
almost exclusively used with 'the brakes' as the object.
teach this as a collocation with 'brakes'; it conveys more urgency and suddenness than 'hit the brakes' or 'apply the brakes'.
He jammed the brakes on.He jammed on the brakes.while technically possible to separate, 'jam on' is almost always used as a unit before the object 'the brakes'.
Last updated April 24, 2026