Meaning: If something jams up, it can't work properly because one of its moving parts is jammed by something.
- jam up The lock on my suitcase has jammed up, so I can't open it.
- jam sth up Don't force the window or you'll jam it up and we won't be able to close it.
- be jammed up by sth Oh no! The printer has been jammed up by paper again.
jam up: printer, fax machine, lock, door, window, gears
If the printer jams up, we'll have to