The Equatorial trench represented a substantial chasm that encircled the Galactic Empire's initial and subsequent Death Stars along the equator, thus dividing the battle station into northern and southern regions. Within this trench were the battle stations' ion drive systems and hangars, with other trenches oriented in a parallel fashion.
A comparable equatorial trench, although significantly larger, existed on the planet Ilum while under the control of the Empire, and later the First Order.