The Collaborative International Dictionary of English v.0.48:

Nautical \Nau"tic*al\, a. [L. nauticus, Gr. naytiko`s, fr.
   nay`ths a seaman, sailor, fr. nay^s ship: cf. F. nautique.
   See Nave of a church.]
   Of or pertaining to seamen, to the art of navigation, or to
   ships; as, nautical skill.
   [1913 Webster]

   Syn: Naval; marine; maritime. See Naval.
        [1913 Webster]

   Nautical almanac. See under Almanac.

   Nautical distance, the length in nautical miles of the
      rhumb line joining any two places on the earth's surface.


   nautical mile. See under Mile.
      [1913 Webster]

WordNet (r) 3.0 (2006):

nautical
    adj 1: relating to or involving ships or shipping or navigation
           or seamen; "nautical charts"; "maritime law"; "marine
           insurance" [syn: nautical, maritime, marine]

Moby Thesaurus II by Grady Ward, 1.0:

23 Moby Thesaurus words for "nautical":
   bathymetric, bathyorographical, boating, deep-sea, hydrographic,
   marine, maritime, naval, navigational, ocean-going, oceanic,
   oceanographic, pelagic, sailing, salty, seafaring, seagoing,
   seamanlike, seamanly, terriginous, thalassic, water-borne,
   yachting