1. Protection from hostile observation and fire by an obstacle such as a hill, ridge, or bank.
2. A vertical distance by which a position is concealed from enemy observation.
3. To shield from enemy fire or observation by using natural or artificial obstacles.
To arrange fortifications in such a way as to provide protection from enfilading (sweeping gunfire) and other fire.
Origin: early 1800s, from French defile (a narrow passage) and -ade (suffix denoting an action or product of an action).