The Collaborative International Dictionary of English v.0.48:

marine mine \ma*rine" mine`\, n. (Mil.)
   A military explosive device designed to be placed on or under
   the surface of a body of water, and to explode when ships
   pass nearby or come in contact with it. Its function is to
   destroy enemy ships or deny hostile naval forces access to
   certain areas of the sea, usually near the shoreline. Also
   called underwater mine and floating mine, and previously
   referred to as a torpedo (See torpedo[2]
   (a) ).
       [PJC]

The Collaborative International Dictionary of English v.0.48:

Torpedo \Tor*pe"do\, n.; pl. Torpedoes. [L. torpedo, -inis,
   from torpere to be stiff, numb, or torpid. See Torpid.]
   [1913 Webster]
   1. (Zool.) Any one of numerous species of elasmobranch fishes
      belonging to Torpedo and allied genera. They are related
      to the rays, but have the power of giving electrical
      shocks. Called also crampfish, and numbfish. See
      Electrical fish, under Electrical.
      [1913 Webster]

   Note: The common European torpedo (Torpedo vulgaris) and
         the American species (Torpedo occidentalis) are the
         best known.
         [1913 Webster]

   2. An engine or machine for destroying ships by blowing them
      up; a mine[4]. Specifically:
      [1913 Webster +PJC]
      (a) A quantity of explosives anchored in a channel,
          beneath the water, or set adrift in a current, and so
          designed that they will explode when touched or
          approached by a vessel, or when an electric circuit is
          closed by an operator on shore; now called marine
          mine. [obsolete]
          [1913 Webster +PJC]

                Damn the torpedoes -- full speed ahead! --Adm.
                                                  David Glasgow
                                                  Farragut (At
                                                  the battle of
                                                  Mobile Bay,
                                                  1864).
      (b) A kind of small submarine boat carrying an explosive
          charge, and projected from a ship against another ship
          at a distance, or made self-propelling, and otherwise
          automatic in its action against a distant ship.
          [1913 Webster]

   3. (Mil.) A kind of shell or cartridge buried in earth, to be
      exploded by electricity or by stepping on it; now called
      land mine. [obsolete]
      [1913 Webster +PJC]

   4. (Railroad) A kind of detonating cartridge or shell placed
      on a rail, and exploded when crushed under the locomotive
      wheels, -- used as an alarm signal.
      [1913 Webster]

   5. An explosive cartridge or shell lowered or dropped into a
      bored oil well, and there exploded, to clear the well of
      obstructions or to open communication with a source of
      supply of oil.
      [1913 Webster]

   6. A kind of firework in the form of a small ball, or pellet,
      which explodes when thrown upon a hard object.
      [1913 Webster]

   7. An automobile with a torpedo body. [Archaic Cant]
      [Webster 1913 Suppl. +PJC]

   Fish torpedo, a spindle-shaped, or fish-shaped,
      self-propelling submarine torpedo.

   Spar torpedo, a canister or other vessel containing an
      explosive charge, and attached to the end of a long spar
      which projects from a ship or boat and is thrust against
      an enemy's ship, exploding the torpedo.

   Torpedo boat, a vessel adapted for carrying, launching,
      operating, or otherwise making use of, torpedoes against
      an enemy's ship., especially, a small, fast boat with
      tubes for launching torpedoes.

   Torpedo nettings, nettings made of chains or bars, which
      can be suspended around a vessel and allowed to sink
      beneath the surface of the water, as a protection against
      torpedoes.
      [1913 Webster]

WordNet (r) 3.0 (2006):

marine mine
    n 1: an explosive mine designed to destroy ships that bump into
         it [syn: floating mine, marine mine]