The noun has 2 meanings:
Meaning #1:
a submersible warship usually armed with torpedoes
Synonyms: pigboat, sub, U-boat
Meaning #2:
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
Synonyms: bomber, grinder, hero, hero sandwich, hoagie, hoagy, Cuban sandwich, Italian sandwich, poor boy, sub, submarine sandwich, torpedo, wedge, zep
The verb submarine has 5 meanings:
Meaning #1:
move forward or under in a sliding motion
Meaning #2:
throw with an underhand motion, as of a baseball
Meaning #3:
bring down with a blow to the legs, in sports
Meaning #4:
control a submarine
Meaning #5:
attack by submarine
The adjective submarine has one meaning:
Meaning #1:
beneath the surface of the sea
Synonym: undersea


