roller coaster

a small gravity railroad, especially in an amusement park, having a train with open cars that moves along a high, sharply winding trestle built with steep inclines that produce sudden, speedy plunges for thrill-seeking passengers.

a car or train of cars for such a railroad.

any phenomenon, period, or experience of persistent or violent ups and downs, as one fluctuating between prosperity and recession or elation and despair.