boat train vs railroad train

boat train and railroad train both are nouns.

Word	Noun	Adjective	Verb	Adverb
boat train	Yes	No	No	No
railroad train	Yes	No	No	No

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

boat train: a train taking passengers to or from a port
railroad train: public transport provided by a line of railway cars coupled together and drawn by a locomotive

Other hypernyms of boat train include train.

boat train (noun)	railroad train (noun)
a train taking passengers to or from a port	public transport provided by a line of railway cars coupled together and drawn by a locomotive