big dipper vs elevated railroad

big dipper and elevated railroad both are nouns.

Word	Noun	Adjective	Verb	Adverb
big dipper	Yes	No	No	No
elevated railroad	Yes	No	No	No

As nouns, elevated railroad is a hypernym of big dipper; that is, elevated railroad is a word with a broader meaning than big dipper:

big dipper: elevated railway in an amusement park (usually with sharp curves and steep inclines)
elevated railroad: a railway that is powered by electricity and that runs on a track that is raised above the street level

Other hypernyms of big dipper include el, elevated, elevated railway, overhead railway, ride.

big dipper (noun)	elevated railroad (noun)
elevated railway in an amusement park (usually with sharp curves and steep inclines)	a railway that is powered by electricity and that runs on a track that is raised above the street level