Source : Webster's Revised Unabridged Dictionary (1913)

Jag \Jag\, n. [Prob. of Celtic origin; cf. W. gag aperture,
   cleft, chink; akin to Ir. & Gael. gag.] [Written also
   {jagg}.]
   1. A notch; a cleft; a barb; a ragged or sharp protuberance;
      a denticulation.

            Arethuss arose . . . From rock and from jag.
                                                  --Shelley.

            Garments thus beset with long jags.   --Holland.

   2. A part broken off; a fragment. --Bp. Hacket.

   3. (Bot.) A cleft or division.

   {Jag bolt}, a bolt with a nicked or barbed shank which
      resists retraction, as when leaded into stone.

Jag \Jag\, v. t. [imp. & p. p. {Jagged}; p. pr. & vb. n.
   {Jagging}.]
   To cut into notches or teeth like those of a saw; to notch.
   [Written also {jagg}.]

   {Jagging iron}, a wheel with a zigzag or jagged edge for
      cutting cakes or pastry into ornamental figures.

Jag \Jag\, n. [Scot. jag, jaug, a leather bag or wallet, a
   pocket. Cf. {Jag} a notch.]
   A small load, as of hay or grain in the straw, or of ore.
   [Prov. Eng. & Colloq. U.S.] [Written also {jagg}.] --Forby.

Jag \Jag\, v. t.
   To carry, as a load; as, to jag hay, etc. [Prov. Eng. &
   Colloq. U.S.]

Jag \Jag\, n.
   1. A leather bag or wallet; pl., saddlebags. [Scot.]

   2. Enough liquor to make a man noticeably drunk; a small
      ``load;'' a time or case of drunkeness; -- esp. in phr. To
      have a jag on, to be drunk. [Slang, U. S. & Dial. Eng.]

Source : WordNet®

jag
     v : cut teeth into; make a jagged cutting edge
     [also: {jagging}, {jagged}]

jag
     n 1: a sharp projection on an edge or surface; "he clutched a jag
          of the rock"
     2: a slit in a garment that exposes material of a different
        color underneath; used in Renaissance clothing
     3: a flap along the edge of a garment; used in medieval
        clothing [syn: {dag}]
     4: a bout of drinking or drug taking
     [also: {jagging}, {jagged}]