diner vs dining car

diner and dining car both are nouns.

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

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

Other synonyms of diner include buffet car, dining compartment.

diner (noun)	dining 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)