What is "to flash in the pan"

Flash \Flash\ (fl[a^]sh), v. i. [imp. & p. p. Flashed (fl[a^]sht); p. pr. & vb. n. Flashing.] [Cf. OE. flaskien, vlaskien to pour, sprinkle, dial. Sw. flasa to blaze, E. flush, flare.]

1. To burst or break forth with a sudden and transient flood of flame and light; as, the lighting flashes vividly; the powder flashed.

2. To break forth, as a sudden flood of light; to burst instantly and brightly on the sight; to show a momentary brilliancy; to come or pass like a flash.

   Names which have flashed and thundered as the watch words of unnumbered struggles.
   --Talfourd.

   The object is made to flash upon the eye of the mind.
   --M. Arnold.

   A thought flashed through me, which I clothed in act.
   --Tennyson.

3. To burst forth like a sudden flame; to break out violently; to rush hastily.

   Every hour He flashes into one gross crime or other.
   --Shak.

   flash in the pan, a failure or a poor performance, especially after a normal or auspicious start; also, a person whose initial performance appears augur success but who fails to achieve anything notable. From 4th pan, n., sense 3 -- part of a flintlock. Occasionally, the powder in the pan of a flintlock would flash without conveying the fire to the charge, and the ball would fail to be discharged. Thus, a good or even spectacular beginning that eventually achieves little came to be called a flash in the pan.

   To flash in the pan, to fail of success, especially after a normal or auspicious start. [Colloq.] See under Flash, a burst of light.
   --Bartlett.

   Syn: Flash, Glitter, Gleam, Glisten, Glister.

   Usage: Flash differs from glitter and gleam, denoting a flood or wide extent of light. The latter words may express the issuing of light from a small object, or from a pencil of rays. Flash differs from other words, also, in denoting suddenness of appearance and disappearance. Flashing differs from exploding or disploding in not being accompanied with a loud report. To glisten, or glister, is to shine with a soft and fitful luster, as eyes suffused with tears, or flowers wet with dew.