pigboat pigboat /ˈpɪgboʊt/

noun

1. A submersible warship usually armed with torpedoes  ( pigboat , sub [Informal] , U-boat , submarine )
   a submersible warship usually armed with torpedoes
    The USS Nautilus was the world's first operational nuclear-powered submarine
   The USS Nautilus was the world's first operational nuclear-powered submarine