1) Ray 
• (n.) A European skate (Raia clavata) having thornlike spines on its back. • (n.) The large European spider crab or king crab (Maia squinado).
Thorn'back` noun 1. (Zoology) A European skate ( Raia clavata ) having thornlike spines on its back. 2. (Zoology) The large European spider crab or king crab ( Maia squinado ). 
USS Thornback was an American Balao Class submarine of 1525 tons displacement launched in 1944. USS Thornback was powered by diesel engines providing a top speed of 21 knots, carried a complement of 75 and was armed with one 4-inch gun, two 20 mm Oerlikon anti-aircraft guns; six 21 inch bow torpedo tubes and four 21 inch stern torpedo tubes.Thornback was 17th century slang for an old maid; an elderly unmarried woman.