The Collaborative International Dictionary of English v.0.48:

Flashing \Flash"ing\, n.
   1. (Engineering) The creation of an artificial flood by the
      sudden letting in of a body of water; -- called also
      flushing.
      [1913 Webster]

   2. (Arch.) Pieces of metal, built into the joints of a wall,
      so as to lap over the edge of the gutters or to cover the
      edge of the roofing; also, similar pieces used to cover
      the valleys of roofs of slate, shingles, or the like. By
      extension, the metal covering of ridges and hips of roofs;
      also, in the United States, the protecting of angles and
      breaks in walls of frame houses with waterproof material,
      tarred paper, or the like. Cf. Filleting.
      [1913 Webster]

   3. (Glass Making)
      (a) The reheating of an article at the furnace aperture
          during manufacture to restore its plastic condition;
          esp., the reheating of a globe of crown glass to allow
          it to assume a flat shape as it is rotated.
      (b) A mode of covering transparent white glass with a film
          of colored glass. --Knight.
          [1913 Webster]

   Flashing point (Chem.), that degree of temperature at which
      a volatile oil gives off vapor in sufficient quantity to
      burn, or flash, on the approach of a flame, used as a test
      of the comparative safety of oils, esp. kerosene; a
      flashing point of 100[deg] F. is regarded as a fairly safe
      standard. The burning point of the oil is usually from ten
      to thirty degree above the flashing point of its vapor.
      Usually called flash point.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Flash point \Flash" point`\, n.
   1. the lowest temperature at which the vapors given off by a
      volatile liquid exposed to air will burst into flame when
      approached by a flame. Also called flashing point.
      [PJC]

   2. That point in time or that degree of provocation at which
      someone will suddenly begin to act vigorously; -- often
      used in reference to angry reactions.
      [PJC]

WordNet (r) 3.0 (2006):

flash point
    n 1: point at which something is ready to blow up [syn: flash
         point, flashpoint]
    2: the lowest temperature at which the vapor of a combustible
       liquid can be ignited in air [syn: flash point,
       flashpoint]