(military) A narrow passage or way (originally , one which soldiers could only march through in a single file or line), especially a narrow gorge or pass between mountains.

(military) A noun "defile" represents an act of marching in files or lines, or a single file of soldiers.

(military, rare) An act of defilading a fortress or other place, or of raising the exterior works in order to protect the interior.

(transitive) Make someone or something physically dirty or unclean, morally impure or unclean, act inappropriately towards or vandalize something sacred or special, or cause something or someone to become ritually unclean.

(transitive, military, rare) Synonym of defilade (“to fortify (something) as a protection from enfilading fire”)