Source : Webster's Revised Unabridged Dictionary (1913)

Jam \Jam\, n. (Mining)
   See {Jamb}.

Jam \Jam\, v. t. [imp. & p. p. {Jammed}; p. pr. & vb. n.
   {Jamming}.] [Either fr. jamb, as if squeezed between jambs,
   or more likely from the same source as champ See {Champ}.]
   1. To press into a close or tight position; to crowd; to
      squeeze; to wedge in.

            The . . . jammed in between two rocks. --De Foe.

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

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

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.

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

Jam \Jam\, n. [Per. or Hind. j[=a]mah garment, robe.]
   A kind of frock for children.

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; as,
   raspberry jam; currant jam; grape jam.

   {Jam nut}. See {Check nut}, under {Check}.

   {Jam weld} (Forging), a butt weld. See under {Butt}.

Source : WordNet®

jam
     v 1: press tightly together or cram; "The crowd packed the
          auditorium" [syn: {throng}, {mob}, {pack}, {pile}]
     2: push down forcibly; "The driver jammed the brake pedal to
        the floor"
     3: crush or bruise; "jam a toe" [syn: {crush}]
     4: interfere with or prevent the reception of signals; "Jam the
        Voice of America"; "block the signals emitted by this
        station" [syn: {block}]
     5: get stuck and immobilized; "the mechanism jammed"
     6: crowd or pack to capacity; "the theater was jampacked" [syn:
         {jampack}, {ram}, {chock up}, {cram}, {wad}]
     7: block passage through; "obstruct the path" [syn: {obstruct},
         {obturate}, {impede}, {occlude}, {block}, {close up}]
        [ant: {free}]
     [also: {jamming}, {jammed}]

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}, {mess}, {muddle}, {pickle}, {kettle of fish}]
     3: a dense crowd of people [syn: {crush}, {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}]
     [also: {jamming}, {jammed}]

Source : Free On-Line Dictionary of Computing

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.

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)