The Collaborative International Dictionary of English v.0.48:

Blowgun \Blow"gun`\, n.
   A tube, as of cane or reed, sometimes twelve feet long,
   through which an arrow (sometimes poisoned) or other
   projectile may be impelled by the force of the breath. It is
   a weapon much used by certain Indians of America and the West
   Indies; -- called also blowpipe, and blowtube. See
   Sumpitan.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Blowtube \Blow"tube`\, n.
   1. A blowgun. --Tylor.
      [1913 Webster]

   2. A similar instrument, commonly of tin, used by boys for
      discharging paper wads and other light missiles.
      [1913 Webster]

   3. (Glassmaking) A long wrought iron tube, on the end of
      which the workman gathers a quantity of "metal" (melted
      glass), and through which he blows to expand or shape it;
      -- called also blowing tube, and blowpipe.
      [1913 Webster]

WordNet (r) 3.0 (2006):

blowtube
    n 1: a tube that directs air or gas into a flame to concentrate
         heat [syn: blowtube, blow tube, blowpipe]
    2: a tube through which darts can be shot by blowing [syn:
       blowgun, blowpipe, blowtube, blow tube]