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]

WordNet (r) 3.0 (2006):

blowgun
    n 1: a tube through which darts can be shot by blowing [syn:
         blowgun, blowpipe, blowtube, blow tube]

Moby Thesaurus II by Grady Ward, 1.0:

24 Moby Thesaurus words for "blowgun":
   automatic, bellows, blower, blowpipe, blowtube, firearm,
   flamethrower, gat, gun, handgun, heater, musket, peashooter, piece,
   pistol, repeater, revolver, rifle, rod, sawed-off shotgun,
   shooting iron, shotgun, six-gun, six-shooter