Topic: BROADCASTING
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| Date: | 1700-1800 |
| Origin: | Perhaps copying the action |
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jam2 past tense and past participle jammed, present participle jamming
1 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.
push hard
[transitive always + adverb/preposition]
He jammed his foot on the accelerator and the car sped off.A chair had been jammed up against the door.2 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.
machine
[intransitive and transitive] also jam upThe front roller has jammed on the photocopier.3 if a lot of people or vehicles jam a place, they fill it so that it is difficult to move [= cram]: Crowds jammed the entrance to the stadium. ➔ jammed (2)
block
[intransitive and transitive] also jam upCrowds jammed the entrance to the stadium.4 to play music in an informal way with other people ➔ jam session
music
[intransitive] also jam outAPM6 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.
jam somebody's/the switchboard
TCTViewers jammed the switchboard with complaints.7 to deliberately prevent broadcasts or other electronic signals from being received, by broadcasting signals on the same wavelength
radio
[transitive]TCB8 used to say that someone is doing something very quickly or well
