Definition of: lightning

(līt′ning) noun
1. A sudden flash of light caused by the discharge of electricity between two electrified regions of cloud, or between a cloud and the earth.
2. The discharge itself.
—ball lightning A luminous, electrically charged sphere, usually less than a foot across, which sometimes appears during a thunderstorm, moving slowly and generally discharging on contact.
—chain lightning Lightning discharged in swift, long strokes, forked or jagged in appearance.
—adjective Fast; rapid: a lightning movement. [Earlier lightening <lighten flash]