Mine

Mine (Naval), a case, usually of iron or steel, which being charged with explosive material can be sunk or submerged in a ship channel in such manner as to endanger any hostile vessel that may attempt to pass over it. A mine may be arranged to be discharged by electricity transmitted by means of a cable from an observation station on shore or shipboard, or by the striking against it of any heavy body. Mines which are not moored, but which are allowed to drift, are towed, are automobile, or are by any method taken or sent through the water expressly to do this work, are known as torpedoes. The explosive commonly used in British service mines of all classes is gun-cotton. [Mining.]