Source : Webster's Revised Unabridged Dictionary (1913)

Bombardier \Bom`bar*dier"\, n. [F. bombardier.] (Mil.)
   (a) One who used or managed a bombard; an artilleryman; a
       gunner. [Archaic]
   (b) A noncommissioned officer in the British artillery.

   {Bombardier beetle} (Zo["o]l.), a kind of beetle ({Brachinus
      crepitans}), so called because, when disturbed, it makes
      an explosive discharge of a pungent and acrid vapor from
      its anal glands. The name is applied to other related
      species, as the {B. displosor}, which can produce ten or
      twelve explosions successively. The common American
      species is {B. fumans}.

Source : WordNet®

bombardier beetle
     n : beetle that ejects audibly a pungent vapor when disturbed