What is "flashing light"

Flash \Flash\, n.; pl. Flashes.

1. A sudden burst of light; a flood of light instantaneously appearing and disappearing; a momentary blaze; as, a flash of lightning.

2. A sudden and brilliant burst, as of wit or genius; a momentary brightness or show.

   The flash and outbreak of a fiery mind.
   --Shak.

   No striking sentiment, no flash of fancy.
   --Wirt.

3. The time during which a flash is visible; an instant; a very brief period.

   The Persians and Macedonians had it for a flash.
   --Bacon.

4. A preparation of capsicum, burnt sugar, etc., for coloring and giving a fictitious strength to liquors.

5. a lamp for providing intense momentary light to take a photograph; as, to take a picture without a flash.

   Syn: flashbulb, photoflash, flash lamp, flashgun.

6. Same as flashlight. [informal]

7. (Journalism) A short news item providing recently received and usually preliminary information about an event that is considered important enough to interrupt normal broadcasting or other news delivery services; also called a news flash or bulletin.

   Flash light, or Flashing light, a kind of light shown by lighthouses, produced by the revolution of reflectors, so as to show a flash of light every few seconds, alternating with periods of dimness.
   --Knight.

   Flash in the pan, the flashing of the priming in the pan of a flintlock musket without discharging the piece; hence, sudden, spasmodic effort that accomplishes nothing.