dining car vs buffet car

dining car and buffet car both are nouns.

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

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

dining car and buffet car: a passenger car where food is served in transit

Other synonyms of dining car include diner, dining compartment.

dining car (noun)	buffet car (noun)
a passenger car where food is served in transit	a passenger car where food is served in transit