We don't have synonyms for fiber gun yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are finger gun.
(n) :
A kind of steam gun for converting, wood, straw, etc., into fiber. The material is shut up in the gun with steam, air, or gas at a very high pressure which is then suddenly relieved by letting a lid at the muzzle fly open, when the rapid expansion separates the fibers.
(n) :
A kind of steam gun for converting, wood, straw, etc., into fiber. The material is shut up in the gun with steam, air, or gas at a very high pressure which is then suddenly relieved by letting a lid at the muzzle fly open, when the rapid expansion separates the fibers.