N-COUNT
许多急转突变;忽好忽坏
If you say that someone or something is on a roller coaster, you mean that they go through many sudden or extreme changes in a short time.
例句
I've been on an emotional roller-coaster since I've been here...
自从我到了这里，情绪就起伏不定。
Over the last few years Japan's socialists have seen their electoral popularity take a roller-coaster ride.
在过去的几年里，日本社会党在选民中的支持率忽高忽低。