1 a : to fill (a place) completely [+ obj] ▪ Thousands of people jammed the hall. = The hall was jammed [=jam-packed, packed] with thousands of people. [no obj] ▪ Thousands of people jammed into the hall.
b [+ obj] : to fill (something, such as a door or a road) so that movement is slow or stopped
▪ People were jamming the exits after the concert. ▪ All the roads and bridges were jammed (with traffic). — sometimes used figuratively ▪ All the telephone lines were jammed with calls from angry customers. 2 a [+ obj] : to press or push (an object) into a tight place
▪ He jammed the book back into the bookcase. ▪ A piece of paper got/was jammed [=stuck] in the copy machine.
b : to push (a part of your body, a lever, etc.) suddenly and forcefully [+ obj] ▪ She jammed her foot down hard on the brakes. [no obj] ▪ She jammed on the brakes.
c [+ obj] : to cause (a part of your body) to be painfully crushed, squeezed, etc.
▪ I jammed my finger in the car door. = My finger got jammed in the car door. = I got my finger jammed in the car door. ▪ I jammed [=stubbed] my toe on the chair's leg. 3 a [no obj] : to stop working properly because something inside prevents movement
▪ The copy machine jammed (up) again. ▪ The lock/gun jammed.
b [+ obj] : to cause (something) to stop working properly by preventing its parts from moving
▪ A piece of paper jammed the copy machine. 4 [+ obj] : to make (a radio signal or broadcast) impossible to understand by sending out signals or messages that weaken or block it
▪ jam a radio broadcast 5 [no obj] : to play music informally together without preparation
▪ We like to get together and jam (with each other). 6 [+ obj] baseball : to throw a pitch that is close to a batter and that the batter is unable to hit well
▪ The pitcher jammed him with an inside fastball.