The Collaborative International Dictionary of English v.0.48:

fo'c'sle \fo'c'sle\, fo'c's'le \fo'c's'le\(f[=o]k"s'l), n.
   The forecastle, a superstructure in the bow of a merchant
   ship where the crew is housed; -- the spelling is intended to
   reflect the common pronunciation among seamen.

   Syn: forecastle.
        [WordNet 1.5 +PJC]