Definition of "Distortion" :

noun: the mistake of misrepresenting the facts

noun: the act of distorting something so it seems to mean something it was not intended to mean

noun: a change for the worse

noun: an optical phenomenon resulting from the failure of a lens or mirror to produce a good image

noun: a change (usually undesired) in the waveform of an acoustic or analog electrical signal; the difference between two measurements of a signal (as between the input and output signal)

"Heavy metal guitar players use vacuum tube amplifiers to produce extreme distortion."

noun: a shape resulting from distortion