to press, squeeze, or wedge tightly between bodies or surfaces, so that motion or extrication is made difficult or impossible: The ship was jammed between two rocks.
to bruise or crush by squeezing: She jammed her hand in the door.
to fill too tightly; cram: He jammed the suitcase with clothing.
to press, push, or thrust violently, as into a confined space or against some object: She jammed her foot on the brake.
to fill or block up by crowding; pack or obstruct: Crowds jammed the doors.
to put or place in position with a violent gesture (often followed by on): He jammed his hat on and stalked out of the room.
to make (something) unworkable by causing parts to become stuck, blocked, caught, displaced, etc.: to jam a lock.
Radio.
to interfere with (radio signals or the like) by sending out other signals of approximately the same frequency.
(of radio signals or the like) to interfere with (other signals).
to play (a piece) in a freely improvised, swinging way; jazz up: to jam both standard tunes and the classics.
Nautical. to head (a sailing ship) as nearly as possible into the wind without putting it in stays or putting it wholly aback.
verb (used without object),jammed,jam·ming.
to become stuck, wedged, fixed, blocked, etc.: This door jams easily.
to press or push, often violently, as into a confined space or against one another: They jammed into the elevator.
(of a machine, part, etc.) to become unworkable, as through the wedging or displacement of a part.
"to press tightly," also "to become wedged," 1706, of unknown origin, perhaps a variant of champ (v.). Of a malfunction in the moving parts of machinery, by 1851. Sense of "cause interference in radio signals" is from 1914. Related: Jammed; jamming. The adverb is recorded from 1825, from the verb.
jam
n.1
"fruit preserve," 1730s, probably a special use of jam (v.) with a sense of "crush fruit into a preserve."
jam
n.2
"a tight pressing between two surfaces," 1806, from jam (v.). Jazz meaning "short, free improvised passage performed by the whole band" dates from 1929, and yielded jam session (1933); but this is perhaps from jam (n.1) in sense of "something sweet, something excellent." Sense of "machine blockage" is from 1890, which probably led to the colloquial meaning "predicament, tight spot," first recorded 1914.
