1. The study of crystal structure by electron-diffraction methods.
2. The diffraction of electrons when they pass through crystalline matter, useful in the study of the structure of materials.
3. An examination of solid surfaces by observing the diffraction of a stream of electrons on the surfaces.

A diffraction is the bending or spreading out of waves; such as, of sound or light, as they pass around the edge of an obstacle or through a narrow opening as when light passes sharp edges or goes through narrow slits and the rays are deflected and produce fringes of light and dark bands.