From Longman Dictionary of Contemporary Englishroller coasterˈroller ˌcoaster noun [countable] 1 DLOa track with very steep slopes and curves, which people ride on in small carriages at fairs and amusement parks2 CONTROL#a situation that changes often Their relationship was an emotional roller coaster.
Examples from the Corpus
roller coaster• All entrepreneurs do it from time to time, just as you would on a roller coaster.• Soon the road resembles a roller coaster track.• I would like to get off the emotional roller coaster I've been on.• This powerful range of feelings, this emotional roller coaster, is normal.• When you buy stock in a company, you are volunteering to ride the roller coaster of risk and rewards.From Longman Business Dictionaryroller coasterˈroller ˌcoaster noun [singular] journalismFINANCE when there are large up and down movements in the prices of shares, currencies etc within a short period of timeAfter a roller-coaster day, the dollar was down against the pound but up moderately against the yen. 