An oceanic trench is a deep, linear depression in the ocean floor formed by the subduction of one tectonic plate beneath another. Trenches are significant in geology for understanding subduction zones, plate tectonics, and the processes that lead to volcanic arcs and earthquake activity.
Reference: Hilde, T. W. C., Uyeda, S., & Kroenke, L. W. (1977). “Evolution of the Western Pacific and Its Margin.” Tectonophysics, 38(1-2), 145-165.