Source : Webster's Revised Unabridged Dictionary (1913)

Back-fire \Back"-fire`\, v. i.
   1. (Engin.) To have or experience a back fire or back fires;
      -- said of an internal-combustion engine.

   2. Of a Bunsen or similar air-fed burner, to light so that
      the flame proceeds from the internal gas jet instead of
      from the external jet of mixed gas and air. --
      {Back"-fir`ing}, n.