smoker vs passenger car

smoker and passenger car both are nouns.

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

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

Other hypernyms of smoker include carriage, coach.

smoker (noun)	passenger car (noun)
a passenger car for passengers who wish to smoke	a railcar where passengers ride
a party for men only (or one considered suitable for men only)
a person who smokes tobacco