The Collaborative International Dictionary of English v.0.48:

Zigzag \Zig"zag`\, n. [F. zigzag, G. zickzack, from zacke,
   zacken, a dentil, tooth. Cf. Tack a small nail.]
   [1913 Webster]
   1. Something that has short turns or angles.
      [1913 Webster]

            The fanatics going straight forward and openly, the
            politicians by the surer mode of zigzag. --Burke.
      [1913 Webster]

   2. (Arch.) A molding running in a zigzag line; a chevron, or
      series of chevrons. See Illust. of Chevron, 3.
      [1913 Webster]

   3. (Fort.) See Boyau.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Zigzag \Zig"zag`\, a.
   Having short, sharp turns; running this way and that in an
   onward course.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Zigzag \Zig"zag`\, v. t. [imp. & p. p. Zigzagged; p. pr. & vb.
   n. Zigzagging.]
   To form with short turns.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Zigzag \Zig"zag`\, v. i.
   To move in a zigzag manner; also, to have a zigzag shape.
   --R. Browning.
   [1913 Webster]

WordNet (r) 3.0 (2006):

zigzag
    adv 1: in a zigzag course or on a zigzag path; "birds flew
           zigzag across the blue sky"
    adj 1: having short sharp turns or angles [syn: zigzag, zig-
           zag]
    n 1: an angular shape characterized by sharp turns in
         alternating directions [syn: zigzag, zig, zag]
    v 1: travel along a zigzag path; "The river zigzags through the
         countryside" [syn: zigzag, crank]

The Devil's Dictionary (1881-1906):

ZIGZAG, v.t.  To move forward uncertainly, from side to side, as one
carrying the white man's burden.  (From _zed_, _z_, and _jag_, an
Icelandic word of unknown meaning.)

    He zedjagged so uncomen wyde
    Thet non coude pas on eyder syde;
    So, to com saufly thruh, I been
    Constreynet for to doodge betwene.
                                                               Munwele