jam

1 noun

1 (C, U) a very thick sweet substance made from boiled fruit and sugar and eaten especially on bread; conserve: strawberry jam

2 (C) a situation in which it is difficult or impossible to move because there are so many people, things, cars etc close together: traffic jam: Sorry we're late. We got stuck in a traffic jam.

3 be in a jam informal to be in a difficult or uncomfortable situation

4 jams (plural) AmE brightly coloured trousers that stop above your knee

5 jam tomorrow BrE informal good things that you are promised if you are patient enough to wait for them

—see also: jam session 2 verb

1 PUSH HARD (T) to push something somewhere using a lot of force, or to push too many things into a small place: jam sth into/under/on: I'll never jam all my clothes into one suitcase. | be jammed (up) against sth (=pushed tightly against something)

2 MACHINE also jam up (I, T) if a lock or a moving part of a machine jams, or if you jam it, it no longer works properly because something is preventing it from moving: The front roller has jammed on the photocopier.

3 BLOCK also jam up (T) if a lot of people or vehicles jam a place, they block it so that it is difficult to move: Crowds jammed the entrance to the stadium.

— see also: jammed (2)

4 MUSIC (I) to play music informally with others without practising first

— see also: jam session

5 jam on the brakes to slow down a car suddenly by putting your foot down hard on the brake 1 (1)

6 jam the switchboard if telephone calls jam the switchboard, so many people are telephoning the same organization that its telephone system cannot work properly

7 RADIO (T) to deliberately prevent broadcasts or other electronic signals from being received by sending out noise on the same wavelength

8 sb is jamming AmE spoken used to say that someone is doing something well