WordNet sense 1 (a large sandwich made of a long crusty roll split lengthwise and filled with meats and cheese (and tomato and onion and lettuce and condiments); different names are used in different sections of the United States):

bomber, grinder, hero, hoagie, hoagy, submarine, torpedo, wedge, zep, Cuban sandwich, hero sandwich, Italian sandwich, submarine sandwich

WordNet sense 2 (a submersible warship usually armed with torpedoes):

pigboat, U-boat

WordNet sense 3 (be a substitute):

substitute, fill in