slip coach vs railroad car

slip coach and railroad car both are nouns.

Word	Noun	Adjective	Verb	Adverb
slip coach	Yes	No	No	No
railroad car	Yes	No	No	No

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

slip coach: a railway car at the end of the train; it can be detached without stopping the train
railroad car: a wheeled vehicle adapted to the rails of railroad

Other hypernyms of slip coach include car, railcar, railway car.

slip coach (noun)	railroad car (noun)
a railway car at the end of the train; it can be detached without stopping the train	a wheeled vehicle adapted to the rails of railroad