The Collaborative International Dictionary of English v.0.48:

Jam \Jam\, n.
   1. A mass of people or objects crowded together; also, the
      pressure from a crowd; a crush; as, a jam in a street; a
      jam of logs in a river.
      [1913 Webster]

   2. An injury caused by jamming. [Colloq.]
      [1913 Webster]

   3. A difficult situation; as, he got himself into a jam.
      [informal]
      [PJC]

The Collaborative International Dictionary of English v.0.48:

Jam \Jam\, n. [Prob. fr. jam, v.; but cf. also Ar. jamad ice,
   jelly, j[=a]mid congealed, jamd congelation, ice.]
   A preserve of fruit boiled with sugar and water; also called
   jelly; as, raspberry jam; currant jam; grape jam.
   [1913 Webster]

   Jam nut. See Check nut, under Check.

   Jam weld (Forging), a butt weld. See under Butt.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Jam \Jam\ (j[a^]m), n. [Per. or Hind. j[=a]mah garment, robe.]
   A kind of frock for children.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Jam \Jam\, n. (Mining)
   See Jamb.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Jam \Jam\, v. t. [imp. & p. p. Jammed (j[a^]md); p. pr. & vb.
   n. Jamming.] [Either fr. jamb, as if squeezed between
   jambs, or more likely from the same source as champ See
   Champ.]
   [1913 Webster]
   1. To press into a close or tight position; to crowd; to
      squeeze; to wedge in; to cram; as, rock fans jammed the
      theater for the concert.
      [1913 Webster]

            The ship . . . jammed in between two rocks. --De
                                                  Foe.
      [1913 Webster]

   2. To crush or bruise; as, to jam a finger in the crack of a
      door. [Colloq.]
      [1913 Webster]

   3. (Naut.) To bring (a vessel) so close to the wind that half
      her upper sails are laid aback. --W. C. Russell.
      [1913 Webster]

   4. To block or obstruct by packing too much (people or
      objects) into; as, shoppers jammed the aisles during the
      fire sale.
      [PJC]

   5. (Radio) To interfere with (a radio signal) by sending
      other signals of the same or nearby frequency; as, the
      Soviets jammed Radio Free Europe broadcasts for years
      during the cold war.
      [PJC]

   6. To cause to become nonfunctional by putting something in
      that blocks the movement of a part or parts; as, he jammed
      the drawer by putting in too many loose papers; he jammed
      the lock by trying to pick it.
      [PJC]

The Collaborative International Dictionary of English v.0.48:

Jam \Jam\, v. i.
   2. To become stuck so as not to function; as, the copier
      jammed again.
      [PJC]

   2. (Music) To play an instrument in a jam session.
      [PJC]

   3. To crowd together; -- usually used with together or in;
      as, fifty people jammed into a conference room designed
      for twenty.
      [PJC]

WordNet (r) 3.0 (2006):

jam
    n 1: preserve of crushed fruit
    2: informal terms for a difficult situation; "he got into a
       terrible fix"; "he made a muddle of his marriage" [syn:
       fix, hole, jam, mess, muddle, pickle, kettle of
       fish]
    3: a dense crowd of people [syn: crush, jam, press]
    4: deliberate radiation or reflection of electromagnetic energy
       for the purpose of disrupting enemy use of electronic devices
       or systems [syn: jamming, electronic jamming, jam]
    v 1: press tightly together or cram; "The crowd packed the
         auditorium" [syn: throng, mob, pack, pile, jam]
    2: push down forcibly; "The driver jammed the brake pedal to the
       floor"
    3: crush or bruise; "jam a toe" [syn: jam, crush]
    4: interfere with or prevent the reception of signals; "Jam the
       Voice of America"; "block the signals emitted by this
       station" [syn: jam, block]
    5: get stuck and immobilized; "the mechanism jammed"
    6: crowd or pack to capacity; "the theater was jampacked" [syn:
       jam, jampack, ram, chock up, cram, wad]
    7: block passage through; "obstruct the path" [syn: obstruct,
       obturate, impede, occlude, jam, block, close up]
       [ant: disengage, free]

Moby Thesaurus II by Grady Ward, 1.0:

546 Moby Thesaurus words for "jam":
   Great Mogul, Jell-O, Mogul, a mass of, a world of, abound with,
   afterthought, albumen, arch dam, army, articulate, assault,
   backstop, baffle, bafflement, bamboo curtain, bank, bar, barrage,
   barricade, barrier, batten, batten down, batter, be alive with,
   beam, bear, bear upon, bear-trap dam, bearings, beaver dam, bed,
   bevy, bewilderment, bind, blancmange, blank wall, blind alley,
   blind gut, block, block up, blockade, blockage, bolt, bonnyclabber,
   boom, boost, bother, bottleneck, box, breakwater, breastwork,
   brick wall, brim, bristle with, buck, buckle, buffer, bulkhead,
   bull, bulldoze, bulwark, bump, bump against, bunch, bung, bunt,
   bureaucratic delay, burst with, butt, butt against, butter, button,
   candy, case, catch, caulk, cecum, charge, chink, chock, choke,
   choke off, choke up, choking, choking off, circumstance, clabber,
   clasp, cleat, clip, clog, clog up, close, close off, close tight,
   close up, cloud, cluster, clutch, clutter, cofferdam, cohue,
   comfit, compact, complication, compote, compress, concentrate,
   condense, condition, confection, confectionery, confirm, confiture,
   confoundment, confusion, congest, congestion, conserve,
   consolidate, constipate, constipation, constrict, cork, corner,
   cornstarch, costiveness, cover, covey, cram, crawl with, cream,
   creep with, crowd, crunch, crush, cul-de-sac, curd, dam, dam up,
   dead end, debar, deep-dye, defense, define, delay, delayage,
   delayed reaction, deluge, densen, densify, detention, dig, dike,
   dilemma, discomposure, disconcert, disconcertedness, disconcertion,
   disconcertment, disturbance, ditch, dog, double take, dough,
   dovetail, dragging, drench, drive, drown out, earthwork, egg white,
   elbow, embankment, embarrassing position, embarrassment, embed,
   embolism, embolus, engraft, engrave, enigma, entrench, establish,
   estate, etch, fence, fill, fill to overflowing, fill up,
   fine how-do-you-do, fix, flight, flock, flocks, flood, footing,
   force, foul, found, freight, frosting, galaxy, gate, gaum, gel,
   gelatin, glair, glaze, glop, glue, glut, gluten, gluttonize, goad,
   goo, gook, goop, gorge, gravity dam, groin, ground, gruel, gumbo,
   gunk, hail, halt, hang-up, hasp, heap, hell to pay, hindrance,
   hinge, hitch, hive, hobble, holdup, hole, honey, hook, horde, host,
   hot water, how-do-you-do, hurtle, hustle, hydraulic-fill dam,
   icing, imbroglio, impact, impasse, impediment, implant, impress,
   imprint, infarct, infarction, infix, ingrain, inscribe, interim,
   iron curtain, jab, jam-pack, jell, jelly, jetty, jog, joggle,
   joint, jolt, jostle, lade, lag, lagging, large amount, latch,
   leaping weir, legion, levee, load, loblolly, location, lock, lodge,
   logjam, lot, lots, maharaja, many, marmalade, mass, masses of,
   meringue, mess, milldam, miter, mix, moat, mob, modality, mode,
   molasses, mole, morass, moratorium, mortise, mound, mousse,
   muchness, mucilage, mucus, multiply, multitude, mystery, nail,
   nest, nizam, nonplus, nudge, numbers, obstacle, obstipate,
   obstipation, obstruct, obstruction, occlude, outroar, outshout,
   overburden, overcharge, overfeed, overfill, overflow with,
   overlade, overload, overpower, overstuff, overweight, overwhelm,
   pack, pad, pang, panoply, pap, paperasserie, parapet,
   parlous straits, pass, paste, pause, peg, perplexity, perturbation,
   pickle, pile drive, pin, pinch, place, plant, plight, plug,
   plug up, plurality, poke, porridge, portcullis, position, posture,
   pother, predicament, preserve, press, pretty pass, pretty pickle,
   pretty predicament, print, problem, prod, pudding, pullulate with,
   pulp, punch, puree, push, putty, puzzle, puzzlement, quagmire,
   quandary, quantities, quicksand, quite a few, rabbet, rabble,
   radiate, raja, ram, ram down, ram in, rampart, rana, rank, rattle,
   red tape, red-tapeism, red-tapery, reprieve, respite, retardance,
   retardation, riddle, rivet, roadblock, rob, rock-fill dam, root,
   rout, ruck, run, run against, satiate, saturate, scores, scrape,
   screw, sealing off, seat, seawall, semifluid, semiliquid, send,
   set, set in, settle, sew, shake, shoal, shoulder, shout down,
   shove, shut off, shut out, shut tight, shutter dam, situation,
   size, skewer, slough, slow-up, slowdown, slowness, snap, soak,
   solidify, soup, spate, spile, spot, squab, squash, squeeze,
   squeeze shut, squish, stamp, stanch, standing, staple, starch,
   state, station, status, stay, stay of execution, stench,
   stereotype, stew, stick, stick fast, sticky mess, sticky wicket,
   stifle, stitch, stone wall, stop, stop up, stoppage, stopper,
   stopple, strait, straits, strangle, strangulate, strangulation,
   stress, strike root, stuff, stuff up, suffocate, supercharge,
   supersaturate, surcharge, surfeit, suspension, swamp, swarm,
   swarm with, sweet, sweet stuff, sweetmeat, sweets, syrup, tack,
   take root, tamp, teem with, throng, throng with, thrust, tidy sum,
   tie-up, tight spot, tight squeeze, tightrope, time lag, toggle,
   top off, transmit, treacle, tricky spot, tutti-frutti,
   unassuredness, unholy mess, upset, wad, wait, wall, wedge, weight,
   weir, whipped cream, wicket dam, work, worlds of, zipper



The Free On-line Dictionary of Computing (30 December 2018):

JaM

   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.


The Free On-line Dictionary of Computing (30 December 2018):

jam

   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.

   (1994-12-12)