parlor car vs passenger car

parlor car and passenger car both are nouns.

Word	Noun	Adjective	Verb	Adverb
parlor car	Yes	No	No	No
passenger car	Yes	No	No	No

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

parlor car: a passenger car for day travel; you pay extra fare for individual chairs
passenger car: a railcar where passengers ride

Other hypernyms of parlor car include carriage, coach.

parlor car (noun)	passenger car (noun)
a passenger car for day travel; you pay extra fare for individual chairs	a railcar where passengers ride