“一落千丈”，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 sudden decline，take a nosedive”等。

例句：

自美国入侵以来，总统的声望一落千丈。

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

价格一落千丈。

The price did a free fall.