The Collaborative International Dictionary of English v.0.48:

Binnacle \Bin"na*cle\, n. [For bittacle, corrupted (perh. by
   influence of bin) fr. Pg. bitacola binnacle, fr. L.
   habitaculum dwelling place, fr. habitare to dwell. See
   Habit, and cf. Bittacle.] (Naut.)
   A case or box placed near the helmsman, containing the
   compass of a ship, and a light to show it at night. --Totten.
   [1913 Webster]

WordNet (r) 3.0 (2006):

binnacle
    n 1: a nonmagnetic housing for a ship's compass (usually in
         front of the helm)