Source : Free On-Line Dictionary of Computing

wiggles
     
        [scientific computation] In solving partial differential
        equations by finite difference and similar methods, wiggles
        are sawtooth (up-down-up-down) oscillations at the shortest
        wavelength representable on the grid.  If an algorithm is
        unstable, this is often the most unstable waveform, so it
        grows to dominate the solution.  Alternatively, stable (though
        inaccurate) wiggles can be generated near a discontinuity by a
        Gibbs phenomenon.