distortion, deformation -- (a change for the worse)
distorted shape, distortion -- (a shape resulting from distortion)
aberration, distortion, optical aberration -- (an optical phenomenon resulting from the failure of a lens or mirror to produce a good image)
distortion -- (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")