pigboat vs sub

pigboat and sub both are nouns.

Word	Noun	Adjective	Verb	Adverb
pigboat	Yes	No	No	No
sub	Yes	No	Yes	No

As nouns, pigboat and sub are synonyms defined as:

Other synonyms of pigboat include submarine.

pigboat (noun)	sub (noun)
a submersible warship usually armed with torpedoes	a submersible warship usually armed with torpedoes
	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

pigboat (verb)	sub (verb)
	be a substitute