sub vs submersible warship

sub and submersible warship both are nouns.

Word	Noun	Adjective	Verb	Adverb
sub	Yes	No	Yes	No
submersible warship	Yes	No	No	No

As nouns, submersible warship is a hypernym of sub; that is, submersible warship is a word with a broader meaning than sub:

Other hypernyms of sub include submersible.

sub (noun)	submersible warship (noun)
a submersible warship usually armed with torpedoes	a warship designed to operate under water
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

sub (verb)	submersible warship (verb)
be a substitute