Noun
(meteorology, astronomy) A very rare phenomenon observed in the morning or evening when the sun is crossing or immediately below the horizon, in which a momentary flash of blue light appears above the upper rim of the solar disk, caused by refraction of light in the atmosphere.
(nuclear physics) A phenomenon sometimes observed when a criticality incident occurs in nuclear materials, inducing a discharge of radiation into the environment.
Source: en.wiktionary.orgWhen combined, the enzyme catalyses a reaction on the luciferin — resulting in a signature blue flash that lasts up to around 100 milliseconds. Source: Internet
When she's using her stingers, the electricity arcs in a bright blue flash. Source: Internet