[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.