/di frak"sheuhn/ , n. Physics.
1. the phenomenon exhibited by wave fronts that, passing the edge of an opaque body, are modulated, thereby causing a redistribution of energy within the front: it is detectable in light waves by the presence of a pattern of closely spaced dark and light bands (diffraction pattern) at the edge of a shadow.
2. the bending of waves, esp. sound and light waves, around obstacles in their path.
[ 1665-75; diffraction- (s. of diffractio ) a breaking up, equiv. to L diffract ( us ) broken up (ptp. of diffringere ) + -ion- -ION. See DIF-, FRACTION ]