WordNet sense 1 (a shape resulting from distortion):

distorted shape

WordNet sense 2 (an optical phenomenon resulting from the failure of a lens or mirror to produce a good image):

aberration, optical aberration

WordNet sense 3 (a change for the worse):

deformation

WordNet sense 4 (the act of distorting something so it seems to mean something it was not intended to mean):

torture, overrefinement, straining, twisting