noun
Geographical term for a ridge or line that separates drainage basins; also used in environmental and planning contexts.
この山脈が太平洋側と日本海側の分水嶺になっている。
This mountain range forms the watershed between the Pacific side and the Sea of Japan side.
noun
turning point; watershed moment; moment of truth
Figurative use for a decisive event or period that marks a major change in a situation, career, or history.
あの試合が彼の人生の分水嶺になった。
That match became the turning point of his life.
この選挙は国の将来を決める分水嶺だ。
This election is a watershed moment that will determine the country's future.