sub vs snorkel breather

sub and snorkel breather both are nouns.

Word	Noun	Adjective	Verb	Adverb
sub	Yes	No	Yes	No
snorkel breather	Yes	No	No	No

sub (noun)	snorkel breather (noun)
a submersible warship usually armed with torpedoes	air passage provided by a retractable device containing intake and exhaust pipes; permits a submarine to stay submerged for extended periods of time
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)	snorkel breather (verb)
be a substitute