[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.