Astronomy. the twinkling or tremulous effect of the light of the stars.
Meteorology. any small-scale twinkling or shimmering of objects that are viewed through the atmosphere, caused by an interception of the observer's line of view by inhomogeneities in the atmospheric refractive index.
Physics. a flash of light from the ionization of a phosphor struck by an energetic photon or particle. random fluctuation of the amplitude, phase, or polarization of an electromagnetic wave.