diner vs buffet car

diner and buffet car both are nouns.

Word	Noun	Adjective	Verb	Adverb
diner	Yes	No	No	No
buffet car	Yes	No	No	No

As nouns, diner and buffet car are synonyms defined as:

Other synonyms of diner include dining car, dining compartment.

diner (noun)	buffet car (noun)
a passenger car where food is served in transit	a passenger car where food is served in transit
a restaurant that resembles a dining car
a person eating a meal (especially in a restaurant)