Wasei-eigo from English 'up down'. Used for fluctuations, alternating states, or vertical movement. Often appears in compound terms like アップダウンが激しい (wild fluctuations) or in sports/tech contexts.
wasei-eigo (Japanese-coined English), from up down
Stock prices have been fluctuating wildly lately.
This course has a lot of ups and downs, making it hard to run.