An effect used it many rock songs (Think Nirvana) that makes a guitar sound loud, gritty, and much more 'heavy hitting'
In 'Smells Like Teen Spirit' the opening riff is played clean twice then distortion kicks in.
by Paul April 22, 2004
A sound that is not part of the original signal. Distortion can be a modification of the original signal (intermodulation distortion), or generating new signals that result from the interference of a combination of signals (harmonic distortion). Can be characterized as a roughness, fuzziness, harshness, or stridency in the music. There are many distortions that can be measured: IM (intermodulation distortion), harmonic distortion, and TIM (transient intermediation distortion).
Distortion can cause breakup, where the headphone can’t handle the power or the low frequencies, which causes sound to crack up.
by Monster Cable May 22, 2009