DEFILE (3)

De‐file″ (dē̍‐fīl″ or dē″fīl; 277), n. [[Cf. F. défilé, fr. défiler to defile.]] 1. 1. Any narrow passage or gorge in which troops can march only in a file, or with a narrow front; a long, narrow pass between hills, rocks, etc.
2. 2. (Mil.) The act of defilading a fortress, or of raising the exterior works in order to protect the interior. See Defilade.