Real Dictionary

lightning
uncountable noun: Lightning is the very bright flashes of light in the sky that happen during thunderstorms.

lightning in American English
a flash of light in the sky caused by the discharge of atmospheric electricity from one cloud to another or between a cloud and the earth
like lightning
to give off such a discharge
adjective: of, pertaining to, or resembling lightning, esp. in regard to speed of movement
intransitive verb: to emit a flash or flashes of lightning
noun: a brilliant electric spark discharge in the atmosphere, occurring within a thundercloud, between clouds, or between a cloud and the ground

lightning in British English
noun: a flash of light in the sky, occurring during a thunderstorm and caused by a discharge of electricity, either between clouds or between a cloud and the earth

lightning in Insurance
noun: Lightning is electrical discharges causing very bright flashes of light in the sky and often, when striking the ground, causing severe damage to persons or objects.