caboose vs railroad car

caboose and railroad car both are nouns.

Word	Noun	Adjective	Verb	Adverb
caboose	Yes	No	No	No
railroad car	Yes	No	No	No

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

caboose: a car on a freight train for use of the train crew; usually the last car on the train
railroad car: a wheeled vehicle adapted to the rails of railroad

Other hypernyms of caboose include car, railcar, railway car.

caboose (noun)	railroad car (noun)
a car on a freight train for use of the train crew; usually the last car on the train	a wheeled vehicle adapted to the rails of railroad
the area for food preparation on a ship