n
(a) line of high land where streams on one side flow into one river or sea and streams on the other side flow into a different river or sea 分水线; 分水岭.
(b) (fig 比喻) turning-point in a course of events 事情发展中的转折点
*Her visit to India proved to be a watershed in her life. 她的印度之行成了她一生的转折点.

n[C]
[Date: 1800-1900; Origin: water + shed 'line of high ground' (16-21 centuries) (from Old English scead 'separation'); suggested by German wasserscheide]
an event or time when important changes happen in history or in your life
= turning pointwatershed in
　The 1932 election represented a watershed in American politics.
watershed decision/case etc
　a watershed case on pension rights
the (9 o'clock) watershed
BrE the time in the evening after which television programmes that are not considered suitable for children may be shown in Britain
technical the high land separating two river systems