The Collaborative International Dictionary of English v.0.48:

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.]
   [1913 Webster]

   Jagging iron, a wheel with a zigzag or jagged edge for
      cutting cakes or pastry into ornamental figures.
      [1913 Webster]