roller coaster vs big dipper

roller coaster and big dipper both are nouns.

Word	Noun	Adjective	Verb	Adverb
roller coaster	Yes	No	No	No
big dipper	Yes	No	No	No

As nouns, roller coaster and big dipper are synonyms defined as:

roller coaster and big dipper: elevated railway in an amusement park (usually with sharp curves and steep inclines)

Other synonyms of roller coaster include chute-the-chute.

roller coaster (noun)	big dipper (noun)
elevated railway in an amusement park (usually with sharp curves and steep inclines)	elevated railway in an amusement park (usually with sharp curves and steep inclines)
anything characterized by abrupt and extreme changes (especially up and down)