tunnel vs rabbit warren

tunnel and rabbit warren both are nouns.

Word	Noun	Adjective	Verb	Adverb
tunnel	Yes	No	Yes	No
rabbit warren	Yes	No	No	No

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

tunnel: a hole made by an animal, usually for shelter
rabbit warren: a series of connected underground tunnels occupied by rabbits

Other hyponyms of tunnel include warren.

tunnel (noun)	rabbit warren (noun)
a passageway through or under something, usually underground (especially one for trains or cars)	an overcrowded residential area
a hole made by an animal, usually for shelter	a series of connected underground tunnels occupied by rabbits

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