mountain climber vs adventurer

mountain climber and adventurer both are nouns.

Word	Noun	Adjective	Verb	Adverb
mountain climber	Yes	No	No	No
adventurer	Yes	No	No	No

As nouns, adventurer is a hypernym of mountain climber; that is, adventurer is a word with a broader meaning than mountain climber:

Other hypernyms of mountain climber include venturer, climber.

mountain climber (noun)	adventurer (noun)
someone who climbs mountains	a person who enjoys taking risks
	someone who travels into little known regions (especially for some scientific purpose)