A momentary flash of light WordNet 3.0 & Open English WordNet

In visual perception, flicker is a human-visible change in luminance of an illuminated surface or light source which can be due to fluctuations of the light source itself, or due to external causes such as due to rapid fluctuations in the voltage of the power supply or incompatibility with an external dimmer. Wikipedia

A directly visible change in brightness of a light source Wikipedia Disambiguation

An unsteady flash of light. Wiktionary

A small, shining body, or transient light; a sparkle. Wiktionary