watershed

/ˈwɔː.tə.ʃed/

an event or period that is important because it represents a big change in how people do or think about something

(标志重大变化的)转折点，分界线，分水岭

The year 1969 was a watershed in her life - she changed her career and remarried.

1969年是她人生的一个转折点——她改了行，也再婚了。

I knew that this result could be possibly a watershed moment for physicists.

我知道这一结果可能是物理学家的分水岭。