I. ˈjam ˌsession BrE AmE ( also jam ) noun [countable]
an occasion when ↑ jazz or ↑ rock musicians play music together in an informal way
II. jam 1 S3 /dʒæm/ BrE AmE noun
1 . FOOD [uncountable and countable] a thick sweet substance made from boiled fruit and sugar, eaten especially on bread ⇨ jelly :
strawberry jam
a jam sandwich
jam jars
2 . CARS/PEOPLE [countable] a situation in which it is difficult or impossible to move because there are so many cars or people:
Sorry we’re late. We got stuck in a traffic jam.
3 . MACHINE [countable] a situation in which a machine does not work because something is stopping a part from moving:
It caused a jam in the printer.
4 . DIFFICULT SITUATION [countable usually singular] informal a difficult situation
(be/get) in/out of/into a jam
We became friends after he helped me out of a jam.
5 . MUSIC [countable]
a) a ↑ jam session
b) a song or piece of music, especially one by a ↑ rap or ↑ rock group
6 . kick out the jams American English informal to play ↑ rock music loudly and with a lot of energy or emotion:
Make no mistake – these guys know how to kick out the jams.
7 . jam tomorrow British English informal good things someone promises you, which never happen:
There is an element of ‘jam tomorrow’ about some of the government’s policies.
III. jam 2 BrE AmE verb ( past tense and past participle jammed , present participle jamming )
[ Date: 1700-1800 ; Origin: Perhaps copying the action ]
1 . PUSH HARD [transitive always + adverb/preposition] to push something somewhere using a lot of force, until it can move no further:
He jammed his foot on the accelerator and the car sped off.
A chair had been jammed up against the door.
2 . MACHINE [intransitive and transitive] ( also jam up ) if a moving part of something 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 [intransitive and transitive] ( also jam up ) if a lot of people or vehicles jam a place, they fill it so that it is difficult to move SYN cram :
Crowds jammed the entrance to the stadium.
jam into
They all jammed into the car.
⇨ ↑ jammed (2)
4 . MUSIC [intransitive] ( also jam out ) to play music in an informal way with other people ⇨ ↑ jam session
5 . jam on the brakes to slow down a car suddenly by putting your foot down hard on the ↑ brake
6 . jam sb’s/the switchboard if telephone calls jam the switchboard of an organization, so many people are phoning the organization that it cannot deal with them all:
Viewers jammed the switchboard with complaints.
7 . RADIO [transitive] to deliberately prevent broadcasts or other electronic signals from being received, by broadcasting signals on the same ↑ wavelength
8 . somebody is jamming American English spoken used to say that someone is doing something very quickly or well
jam out phrasal verb
to dance to music