Wavefolding
Distortion in which the part of the waveform that hits the ceiling is folded back down instead of being chopped off.
Where clipping flattens the peak, a wavefolder mirrors it: everything above the threshold is reflected downward, and with more gain it folds again, and again. A sine turns into an ever denser series of creases, and the harmonics grow in a way that sounds glassier than the fizz of a clipped signal. Technically it is a special case of waveshaping with a zigzag transfer curve.
Don Buchla made it central to "west coast" synthesis in the 1970s — start with a simple wave and add harmonics, rather than the east coast's subtractive filtering. It has enjoyed a revival in Eurorack. Digitally it is awkward: the creases generate harmonics far above Nyquist, and without oversampling they fold back down as aliasing. Folding, twice over.