'Roller coaster' definitions:

Definition of 'roller coaster'

(from WordNet)
noun
Anything characterized by abrupt and extreme changes (especially up and down); "the economy has been on a roller coaster all year"
noun
Elevated railway in an amusement park (usually with sharp curves and steep inclines) [syn: roller coaster, big dipper, chute-the-chute]

Definition of 'Roller coaster'

From: GCIDE
  • Roller coaster \Roller coaster\ 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. +PJC]