big dipper vs elevated railway

big dipper and elevated railway both are nouns.

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

As nouns, elevated railway is a hypernym of big dipper; that is, elevated railway 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 railway: 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 railroad, overhead railway, ride.

big dipper (noun)	elevated railway (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