trench -
To excavate an elongated pit for protection of soldiers and or equipment, usually perpendicular to the line of sight toward the enemy.
trench -
To excavate an elongated and often narrow pit.
Wikipedia
A trench is a type of excavation or depression in the ground. Trenches are generally defined by being deeper than they are wide (as opposed to a wider gully or ditch), and by being narrow compared to their length (as opposed to a simple hole).