Light’ning, n.
(līt′ning), n. [For lightening, from lighten, v. i.; A-S. leóhteing, lyhting.]
Sense 1. A discharge of atmospheric electricity, accompanied by a vivid flash of light, commonly from one cloud to another, sometimes from a cloud to the earth. The sound produced by the electricity in passing rapidly through the atmosphere constitutes thunder.
Sense 2. The act of making bright, or the state of being made bright; enlightenment; brightening, as of the mental powers. [Rare.]
Sense 3. [From lighten, to diminish weight.] Abatement; alleviation; mitigation. [Obs.] Spectator.
Ball-lightning, a rare form of lightning, seen as a globe of fire moving from the clouds to the earth.—Chain-lightning, lightning in angular or zigzag, and, often, forked flashes.—Heat-lightning, faint flashes of light without thunder, seen near the horizon, especially at the close of a hot day, as if the effect of a thunder-storm below the horizon.—Lightning-conductor, a lightning-rod.—Sheet-lightning, a diffused glow of electric light flashing out from the clouds, and illumining their outlines.