a. Being, acting, or growing, under water in the sea; as, submarine navigators; submarine plants. [ 1913 Webster ]

Submarine armor, a waterproof dress of strong material, having a helmet into which air for breathing is pumped through a tube leading from above the surface to enable a diver to remain under water. --
Submarine cable. See Telegraph cable, under Telegraph. --
Submarine mine. See Torpedo, 2 (a). [ 1913 Webster ]

n. A submarine plant or animal. [ 1913 Webster ]

n. 1. A submarine boat; a ship that can travel under the surface of the water. Most such ships are ships of war, as part of a navy, but submarines are also used for oceanic research. Also called sub and (from the German U-Boot) U-boat. esp., Nav., a submarine torpedo boat; -- called specif. submergible submarine when capable of operating at various depths and of traveling considerable distances under water, and submersible submarine when capable of being only partly submerged, i.e., so that the conning tower, etc., is still above water. The latter type and most of the former type are submerged as desired by regulating the amount of water admitted to the ballast tanks and sink on an even keel; some of the former type effect submersion while under way by means of horizontal rudders, in some cases also with admission of water to the ballast tanks. [ Webster 1913 Suppl. +PJC ]

2. A stowaway on a seagoing vessel. [ Colloq. ] [ PJC ]

3. A submarine sandwich. [ PJC ]

n. A large sandwich on an elongated roll, usually incompletely cut into two halves, filed with various cold cuts, meatballs, lettuce, cheese, tomatoes, olives, etc., and spiced variously, and often having oil or other dressing applied; called also hoagie, hero, hero sandwich, grinder, sub, submarine, poor boy, and Italian sandwich. A single such sandwich may consitute a substantial meal. Very large variants are sometimes prepared for social gatherings and cut into pieces for individual consumption. [ PJC ]