N-COUNT
許多急轉(zhuǎn)突變;忽好忽壞
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...
自從我到了這里，情緒就起伏不定。
Over the last few years Japan's socialists have seen their electoral popularity take a roller-coaster ride.
在過去的幾年里，日本社會黨在選民中的支持率忽高忽低。