tunnel vs catacomb

tunnel and catacomb both are nouns.

Word	Noun	Adjective	Verb	Adverb
tunnel	Yes	No	Yes	No
catacomb	Yes	No	No	No

As nouns, catacomb is a hyponym of tunnel; that is, catacomb is a word with a more specific, narrower meaning than tunnel:

tunnel: a passageway through or under something, usually underground (especially one for trains or cars)
catacomb: an underground tunnel with recesses where bodies were buried (as in ancient Rome)

Other hyponyms of tunnel include railroad tunnel, subway, underpass.

tunnel (noun)	catacomb (noun)
a passageway through or under something, usually underground (especially one for trains or cars)	an underground tunnel with recesses where bodies were buried (as in ancient Rome)
a hole made by an animal, usually for shelter

tunnel (verb)	catacomb (verb)
force a way through
move through by or as by digging