NOUN (2)

1. abrupt electric discharge from cloud to cloud or from cloud to earth accompanied by the emission of light;

2. 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 Collaborative International Dictionary of English v.0.48:

Lightning \Light"ning\ (l[imac]t"n[i^]ng), n. [For lightening,
   fr. lighten to flash.]
   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.
      [1913 Webster]

   2. The act of making bright, or the state of being made
      bright; enlightenment; brightening, as of the mental
      powers. [R.]
      [1913 Webster]

   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 (Zool.), 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.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Lightning \Light"ning\ (l[imac]t"n[i^]ng), vb. n.
   Lightening. [R.]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

electric current \electric current\, electrical current
\electrical current\,
   the movement of electrically charged particles, atoms, or
   ions, through solids, liquids, gases, or free space; the term
   is usually used of relatively smooth movements of electric
   charge through conductors, whether constant or variable.
   Sudden movements of charge are usually referred to by other
   terms, such as spark or lightning or discharge. In
   metallic conductors the electric current is usually due to
   movement of electrons through the metal. The current is
   measured as the rate of movement of charge per unit time, and
   is counted in units of amperes. As a formal definition, the
   direction of movement of electric current is considered as
   the same as the direction of movement of positive charge, or
   in a direction opposite to the movement of negative charge.
   Electric current may move constantly in a single direction,
   called direct current (abbreviated DC), or may move
   alternately in one direction and then the opposite direction,
   called alternating current (abbreviated AC).
   [PJC]

WordNet (r) 3.0 (2006):

lightning
    n 1: abrupt electric discharge from cloud to cloud or from cloud
         to earth accompanied by the emission of light
    2: 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

Moby Thesaurus II by Grady Ward, 1.0:

49 Moby Thesaurus words for "lightning":
   Jupiter Fulgur, Thor, antelope, arrow, ball lightning, blue darter,
   blue streak, bolt, bolt of lightning, cannonball, chain lightning,
   courser, dark lightning, dart, eagle, electricity, express train,
   fireball, firebolt, flash, flying flame, forked lightning,
   fulguration, fulmination, gazelle, greased lightning, greyhound,
   hare, jet plane, levin bolt, light, mercury,
   oak-cleaving thunderbolts, quicksilver, rocket, scared rabbit,
   sheet lightning, shot, streak, streak of lightning, striped snake,
   stroke of lightning, swallow, thought, thunderball, thunderbolt,
   thunderstroke, torrent, wind



Easton's 1897 Bible Dictionary:

Lightning
   frequently referred to by the sacred writers (Nah. 1:3-6).
   Thunder and lightning are spoken of as tokens of God's wrath (2
   Sam. 22:15; Job 28:26; 37:4; Ps. 135:7; 144:6; Zech. 9:14). They
   represent God's glorious and awful majesty (Rev. 4:5), or some
   judgment of God on the world (20:9).