2. The act of making bright, or the state of being made
bright; enlightenment; brightening, as of the mental
powers. [R.]
{Ball lightning}, a rare form of lightning sometimes seen as
a globe of fire moving from the clouds to the earth.
{Chain lightning}, lightning in angular, zigzag, or forked
flashes.
{Heat lightning}, more or less vivid and extensive flashes of
electric light, without thunder, seen near the horizon,
esp. at the close of a hot day.
{Lightning arrester} (Telegraphy), a device, at the place
where a wire enters a building, for preventing injury by
lightning to an operator or instrument. It consists of a
short circuit to the ground interrupted by a thin
nonconductor over which lightning jumps. Called also
{lightning discharger}.
{Lightning bug} (Zo["o]l.), a luminous beetle. See {Firefly}.
{Lightning conductor}, a lightning rod.
{Lightning glance}, a quick, penetrating glance of a
brilliant eye.
{Lightning rod}, a metallic rod set up on a building, or on
the mast of a vessel, and connected with the earth or
water below, for the purpose of protecting the building or
vessel from lightning.
{Sheet lightning}, a diffused glow of electric light flashing
out from the clouds, and illumining their outlines. The
appearance is sometimes due to the reflection of light
from distant flashes of lightning by the nearer clouds.