adventurer vs spelunker

adventurer and spelunker both are nouns.

Word	Noun	Adjective	Verb	Adverb
adventurer	Yes	No	No	No
spelunker	Yes	No	No	No

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

adventurer: someone who travels into little known regions (especially for some scientific purpose)
spelunker: a person who explores caves

adventurer (noun)	spelunker (noun)
a person who enjoys taking risks	a person who explores caves
someone who travels into little known regions (especially for some scientific purpose)