The Collaborative International Dictionary of English v.0.48:

Extinguisher \Ex*tin"guish*er\, n.
   One who, or that which, extinguishes; esp., a hollow cone or
   other device for extinguishing a flame, as of a torch or
   candle.
   [1913 Webster]

   fire extinguisher a portable device designed to deliver
      chemicals, usually in a stream, that can suppress or
      extinguish a fire. Examples of fire extinghuishers are a
      carbon dioxide extinguisher, or CO2 extinguisher, and
      soda-acid extinguisher.
      [PJC]

WordNet (r) 3.0 (2006):

fire extinguisher
    n 1: a manually operated device for extinguishing small fires
         [syn: fire extinguisher, extinguisher, asphyxiator]

Moby Thesaurus II by Grady Ward, 1.0:

28 Moby Thesaurus words for "fire extinguisher":
   Foamite, acid, automatic sprinkler, carbon tet,
   carbon tetrachloride, carbon-dioxide foam, deck gun, deluge set,
   extinguisher, fire apparatus, fire engine, fire hose, fire hydrant,
   fireplug, foam, foam extinguisher, hook-and-ladder, ladder pipe,
   pumper, snorkel, soda, sprinkler, sprinkler head, sprinkler system,
   super-pumper, water, water cannon, wet blanket