1. roller coaster(n = noun.state) - anything characterized by abrupt and extreme changes (especially up and down); "the economy has been on a roller coaster all year"
is a kind of sturm und drang, turbulence, upheaval
2. roller coaster(n = noun.artifact) big dipper, chute-the-chute - elevated railway in an amusement park (usually with sharp curves and steep inclines);
is a kind of el, elevated, elevated railroad, elevated railway, overhead railway, ride
has particulars: hypercoaster
An amusement railroad of varying design in which open cars coast by gravity over a long winding track in a closed circuit, with steep pitches and ascents, and in some cases loops in which the cars are briefly upside-down; typically, the cars are pulled by a chain device to the top of the first peak, after which gravity and momentum provide the only propulsive forces. In some cases, the cars are suspended from a monorail rather than resting on a track, and such cars may be made to swing outward at an angle near to the horizontal. It is a popular amusement at many amusement parks, but is sufficiently frightening to some people that they refuse to ride in one. [Webster 1913 Suppl.]
coaster, coaster brake, coaster wagon, european roller, garden roller, ground roller, high roller, holy roller, leaf roller, paint roller, pill roller, road roller, roller, roller bandage, roller bearing, roller bit, roller blade, roller blind, roller skate, roller skating, roller towel, squeegee roller