Source : Webster's Revised Unabridged Dictionary (1913)

Forecastle \Fore"cas`tle\ (?; sailors say ?), n. (Naut.)
   (a) A short upper deck forward, formerly raised like a
       castle, to command an enemy's decks.
   (b) That part of the upper deck of a vessel forward of the
       foremast, or of the after part of the fore channels.
   (c) In merchant vessels, the forward part of the vessel,
       under the deck, where the sailors live.

Source : WordNet®

forecastle
     n : living quarters consisting of a superstructure in the bow of
         a merchant ship where the crew is housed [syn: {fo'c'sle}]