# jam on

CEFR B2 · Phrasal verb

Source: https://englishreference.com/word/jam-on
Updated: 2026-04-24

## Definition

to press something down quickly and with a lot of force, usually the brakes of a car.

For teachers: to apply something—typically vehicle brakes—suddenly and forcefully; often used to describe an emergency or reflexive action.

## Examples

- 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.

## Pitfalls

- Not "He jammed the brakes on." but "He jammed on the brakes." — while technically possible to separate, 'jam on' is almost always used as a unit before the object 'the brakes'.

## Usage notes

- almost exclusively used with 'the brakes' as the object.
- Teaching tip: teach this as a collocation with 'brakes'; it conveys more urgency and suddenness than 'hit the brakes' or 'apply the brakes'.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.