a statement that describes something in a way that makes it seem less important, serious, bad, etc. than it really is, or the act of making such statements

To say that her resignation was a shock would be an understatement - it caused panic. 说她辞职令人震惊过于轻描淡写了——实际上引起了恐慌。

"It didn't go well? " "That's the understatement of the year/decade/century. It was a disaster." 事情进展不顺利？“这是本年度／十年来／本世纪最温和的说法。那是场灾难。”