a change for the worse

a shape resulting from distortion

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

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)

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

the mistake of misrepresenting the facts