noun: 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
noun: a submersible warship usually armed with torpedoes
verb: be a substitute
Example: "The young teacher had to substitute for the sick colleague"
name: A surname (very rare: popularity rank in the U.S.: #67417)