noun
oceanic trench; deep-sea trench
A long, narrow, deep depression in the ocean floor; a technical term in geology and oceanography.
マリアナ海溝は世界で最も深い海溝です。
The Mariana Trench is the deepest oceanic trench in the world.
日本海溝では地震が頻繁に
Earthquakes frequently occur along the Japan Trench.