Noun
1. a change for the worse
2. a shape resulting from distortion
3. an optical phenomenon resulting from the failure of a lens or mirror to produce a good image
4. 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"5. the act of distorting something so it seems to mean something it was not intended to mean
6. the mistake of misrepresenting the facts