'Entrenchment' in the Bible

So David set out and went to the place where Saul was camped. David saw the place where Saul and Abner son of Ner, the general in command of his army, were sleeping. Now Saul was lying in the entrenchment, and the army was camped all around him.

So David and Abishai approached the army at night and found Saul lying asleep in the entrenchment with his spear stuck in the ground by his head. Abner and the army were lying all around him.