1 [jam]
verb (used with object), jammed, jamming.
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.
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, jamming.
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.
Jazz. to participate in a jam session.
the act of jamming or the state of being jammed.
a mass of objects, vehicles, etc., jammed together or otherwise unable to move except slowly: a log jam; a traffic jam.
Informal. a difficult or embarrassing situation; fix: He got himself into a jam with his boss.

1700–10; apparently imitative; cf. champ1, dam1

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2 [jam]
a preserve of whole fruit, slightly crushed, boiled with sugar: strawberry jam.
put on jam, Australian Slang. to adopt a self-important manner or use affected speech.

1720–30; perhaps special use of jam1

jamlike, jammy, adjective


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Based on the Random House Dictionary, © Random House, Inc. 2014.
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World English Dictionary
jam1 (dʒæm)
vb (often foll by on) , jams, jamming, jammed
1.  (tr) to cram or wedge into or against something: to jam paper into an incinerator
2.  (tr) to crowd or pack: cars jammed the roads
3.  to make or become stuck or locked: the switch has jammed
4.  to activate suddenly (esp in the phrase jam on the brakes)
5.  (tr) to block; congest: to jam the drain with rubbish
6.  (tr) to crush, bruise, or squeeze; smash
7.  radio to prevent the clear reception of (radio communications or radar signals) by transmitting other signals on the same frequency
8.  slang (intr) to play in a jam session
9.  a crowd or congestion in a confined space: a traffic jam
10.  the act of jamming or the state of being jammed
11.  informal a difficult situation; predicament: to help a friend out of a jam
12.  See jam session
[C18: probably of imitative origin; compare champ1]

jam2 (dʒæm)
1.  a preserve containing fruit, which has been boiled with sugar until the mixture sets
2.  slang something desirable: you want jam on it
3.  jam today the principle of living for the moment
[C18: perhaps from jam1 (the act of squeezing)]

abbreviation for
1.  Jamaica
2.  Bible James

Collins English Dictionary - Complete & Unabridged 10th Edition
2009 © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009
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Word Origin & History

"to press tightly," also "to become wedged," 1706, of unknown origin, perhaps a variant of champ (v.). Sense of "to cause interference in radio signals" is from 1914. Jazz noun meaning "short, free improvised passage performed by the whole band" dates from 1929, and yielded
jam session (1933); perhaps from jam (n.) in sense of "something sweet, something excellent." Noun sense of "machine blockage" is from 1890, which probably led to the colloquial meaning "predicament," first recorded 1914.

"fruit preserve," 1730s, probably a special use of jam (v.) with a sense of "crush fruit into a preserve."
Online Etymology Dictionary, © 2010 Douglas Harper
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American Heritage
Medical Dictionary

jam (jām)
v. jammed, jam·ming, jams

  1. To block, congest, or clog.

  2. To crush or bruise.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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Computing Dictionary

JaM definition

John and Martin. An interpreted FORTH-like graphics language by John Warnock and Martin Newell, Xerox PARC, 1978. JaM was the forerunner of both Interpress and PostScript. It is mentioned in PostScript Language reference Manual, Adobe Systems, A-W 1985.

jam definition

A condition on a network where two nodes transmitting simultaneously detect the collision and continue to transmit for a certain time (4 to 6 bytes on Ethernet) to ensure that the collision has been detected by all nodes involved.

The Free On-line Dictionary of Computing, © Denis Howe 2010 http://foldoc.org
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American Heritage
Abbreviations & Acronyms
The American Heritage® Abbreviations Dictionary, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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American Heritage
Idioms & Phrases


see under get in a bind.

The American Heritage® Dictionary of Idioms by Christine Ammer.
Copyright © 1997. Published by Houghton Mifflin.
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Example sentences
For a full-textured jam with big spoonfuls of berries, mash the fruit coarsely.
The mammoth traffic jam that left thousands of truckers sitting in gridlock for
  more than a week has vanished.
Here's an easy refrigerator jam recipe that's perfect for first-time jam-makers.
Apricot jam and almond paste makes this basic butter cake worthy of its
Idioms & Phrases
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