NOUN (2)

1. an armored pilothouse on a warship;

2. a raised bridge on a submarine; often used for entering and exiting;

The Collaborative International Dictionary of English v.0.48:

Conning tower \Con"ning tow"er\,
   1. n. The shot-proof pilot house of a war vessel. [archaic]
      [1913 Webster]

   2. the raised structure rising above the deck of a submarine.
      [PJC]

WordNet (r) 3.0 (2006):

conning tower
    n 1: an armored pilothouse on a warship
    2: a raised bridge on a submarine; often used for entering and
       exiting