“一落千丈（literally drop a thousand zhang in one fall）”，汉语成语，原形容琴声由高而低突然变化；现在表示下降得很厉害，用来形容声誉、地位或经济状况急剧下降。可以翻译为“suffer a drastic decline”，也可以用“nosedive”来表示。

例句：

自从美国入侵以来，这位总统的声誉一落千丈。

Since the US invasion the president's reputation has nosedived.

由于丑闻，他的声誉一落千丈。

His prestige suffered a disastrous decline because of the scandal.

父亲去世之后的家境一落千丈。

His family’s financial situation has rapidly worsened since the death of his father.