The Collaborative International Dictionary of English v.0.48:

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.
       [1913 Webster]

   Bombardier beetle (Zool.), 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 Brachinus displosor, which can produce
      ten or twelve explosions successively. The common American
      species is Brachinus fumans.
      [1913 Webster]

WordNet (r) 3.0 (2006):

bombardier beetle
    n 1: beetle that ejects audibly a pungent vapor when disturbed