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.