Source : Webster's Revised Unabridged Dictionary (1913)

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.

Source : WordNet®

jamming
     See {jam}

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}]

jamming
     n : deliberate radiation or reflection of electromagnetic energy
         for the purpose of disrupting enemy use of electronic
         devices or systems [syn: {electronic jamming}, {jam}]

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}]