hitchhiker vs passenger

hitchhiker and passenger both are nouns.

Word	Noun	Adjective	Verb	Adverb
hitchhiker	Yes	No	No	No
passenger	Yes	No	No	No

As nouns, passenger is a hypernym of hitchhiker; that is, passenger is a word with a broader meaning than hitchhiker:

hitchhiker: a person who travels by getting free rides from passing vehicles
passenger: a traveler riding in a vehicle (a boat or bus or car or plane or train etc) who is not operating it

Other hypernyms of hitchhiker include rider.

hitchhiker (noun)	passenger (noun)
a person who travels by getting free rides from passing vehicles	a traveler riding in a vehicle (a boat or bus or car or plane or train etc) who is not operating it