The American Heritage® Dictionary of the English Language, 4th Edition
n. Slang A submarine.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
n. a submersible warship usually armed with torpedoes
Word Usage
"A butcher stands in the tail of his pigboat like a Venetian gondolier; a pig's head is nailed to the prow, the rest of the carcass laid out in the anatomically correct order down the length of the boat."