1. Sparkling; a subjective sensation, as of seeing sparks.
2. A tiny flash of light, especially one produced in certain substances (scintillators) when a photon or an ionizing particle deposits energy in the scintillator by ionizing one or more atoms.

Typically there is one scintillation for each ionizing event. The flashes can be counted electronically, and the average count rate then measures the intensity of the incident radiation.

3. The action of scintillating; emission of sparks or spark-like flashes of light; a spark.
4. The twinkling or tremulous motion of the light from fixed stars or a rapid twinkling of stars caused by constant small changes in the atmosphere's density.
5. A small flash of visible or ultraviolet light emitted by fluorescence in a phosphor when it is struck by a charged particle or high-energy photon.
6. Figuratively, a flash, a brilliant display (of wit or thought).

The twinkling of starlight caused by variations of refractivity in high-altitude layers of the earth's atmosphere.

The generic term for scintillation phenomena observed in light that reaches the eyes from sources liying within the Earth's atmosphere: An atmospheric boil, or a scintillation, refers to the rapid fluctuations in the amplitude and phase of electromagnetic or acoustic waves that have propagated through a medium containing fluctuations in refractive index, such as the atmosphere.

The most common example of optical scintillation is the "twinkling" of stars observed through the atmosphere because it arises as a result of random angular scattering produced by refractive index fluctuations.

Fluctuations in the amplitude of different frequency components in the spectrum of an object can give rise to apparent changes in its color (chromatic scintillation). An example is the random red and blue twinkling of bright stars near the horizon.

Scintillation statistics have been used to study turbulence in regions ranging from the planetary boundary layer to the ionosphere, as well as interplanetary and interstellar space and it is important for astronomical imaging, optical and radio communications, laser and acoustical propagation, active and passive remote sensing, and the performance of the Global Positioning System.

The twinkling of stars (fluctuation of intensity) as seen through a planet's atmosphere: Atmospheric scintillation is caused by a star's light being distorted by the Earth's atmosphere and atmospheric scintillation is greater for bright stars that are low on the horizon.

The Sun emits blobs of plasma (known as the solar wind). Depending on the geometry, rays through different blobs can be focused to a single point. A sort of "twinkling" known as interplanetary scintillation can therefore be observed.