The Collaborative International Dictionary of English v.0.48:

Jag \Jag\ (j[a^]g), n. [Prob. of Celtic origin; cf. W. gag
   aperture, cleft, chink; akin to Ir. & Gael. gag.] [Written
   also jagg.]
   [1913 Webster]
   1. A notch; a cleft; a barb; a ragged or sharp protuberance;
      a denticulation.
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            Arethuss arose . . .
            From rock and from jag.               --Shelley.
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            Garments thus beset with long jags.   --Holland.
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   2. A part broken off; a fragment. --Bp. Hacket.
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   3. (Bot.) A cleft or division.
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   4. A leather bag or wallet; pl., saddlebags. [Scot.]
      [Webster 1913 Suppl.]

   5. 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.]
      [Webster 1913 Suppl.]

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