ナイフエッジ

noun

knife edge

Refers to a very thin, sharp edge like that of a knife. Used in both literal and figurative contexts, such as describing a precarious situation or a sharp dividing line.

• その議ぎ論ろんはナイフエッジの上うえを歩あるくようなものだった。

  The debate was like walking on a knife edge.

• ナイフエッジの精せい度どが要よう求きゅうされる部ぶ品ひんだ。

  It's a part that requires knife-edge precision.