abrupt electric discharge from cloud to cloud or from cloud to earth accompanied by the emission of light
"The thunderstorm was marked by a sudden flash of lightning that illuminated the dark sky before rolling thunder followed."
the flash of light that accompanies an electric discharge in the atmosphere (or something resembling such a flash); can scintillate for a second or more
"The sudden lightning flashed across the dark sky, illuminating the storm clouds for just a brief moment before vanishing."
A flash of light produced by short-duration, high-voltage discharge of electricity within a cloud, between clouds, or between a cloud and the earth.
"A sudden bolt of lightning illuminated the stormy sky as it struck the ground below."
In plain English: Lightning is the bright flash of electricity that jumps between clouds during a thunderstorm.
"The sudden flash of lightning scared everyone outside during the storm."
Usage: Use "lightning" to describe both the natural electrical flash in storms and anything that happens with extreme speed or suddenness. Do not confuse this noun for electricity itself, which is a continuous flow rather than a brief discharge.
To produce lightning.
"The powerful storm clouds began to lighten as they produced a brilliant flash of lightning that illuminated the entire valley."
Extremely fast or sudden; moving (as if) at the speed of lightning.
"The thief darted across the room with lightning speed before anyone could react."
"The lightning bolt struck with such force that it looked like solid silver in the dark sky."
The word lightning comes from the verb to lighten combined with the suffix -ing. It is a doublet of the word lightening, meaning both are derived from the same root but developed separately.