Distortion
From Glossary of Meteorology
distortion
Nonrealistic reproduction, or nonideal formation.
In optics, it is an imperfection in an image caused by an imperfection in the optical system by which the image is produced. In electronics, distortion is a change in waveform of a signal that occurs upon passage of the signal through an instrument. Crystal distortion is the expansion of a crystal lattice near any crystal boundary surface.