the occurrence of a natural electrical discharge of very short duration and high voltage between a cloud and the ground or within a cloud, accompanied by a bright flash and typically also thunder:a tremendous flash of lightning
literary a flash or discharge of lightning:the sky was a mass of black cloud out of which lightnings flashed
very quick:a lightning cure for his hangovergalloping across the country at lightning speed
lightning never strikes twice in the same place
proverb an unusual situation or event is unlikely to happen again in exactly the same circumstances or to the same person.
like (greased) lightning
Middle English: special use of lightening (verbal noun from lighten2)