roller coaster
noun[C]
us/ˈroʊ·lər ˌkoʊ·stər/pluralroller coastersasmallrailroad,esp. in anamusementpark, withopencarsthattravelquicklyalong asteep,curvedtrackthat goes up and down over and over
A roller coaster is also afeeling,situation, orexperiencethatchangesveryquickly:
anemotionalroller coaster