dining compartment vs diner

dining compartment and diner both are nouns.

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

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

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

Other synonyms of dining compartment include buffet car, dining car.

dining compartment (noun)	diner (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)