The zig-zag motion of a ball in baseball or of a player in football, or, more generally, an act performed to evade or distract.
The Dickson Baseball Dictionary (Paul Dickson, 1989) describes it thusly:
1. n. A slow, tantalizing curveball.
2. n. Term for any odd-breaking pitch, including a suspected spitball.
Dickson notes about five different spellings and then quotes Edward J. Nichols: "The uncertainty as to spelling is typical of terms invented by the players rather than the sports reporters."