In military terms, a deﬁle is a path so narrow that only a single ﬁle of men can move along it. (In England, the French word was often pronounced with an -ee at the end, but being generally written -e without accent, it has come to be treated as e mute.) In a larger context, deﬁle means a long, narrow, steep-sided pass through hills or mountains, often forming the approach to a larger pass. In The Man Who Killed the Deer, Frank Waters writes: “There where the pines at last stood back to let him pass, he saw rising before him the two rocky points of a parted cliff, between them a steep, narrow deﬁle. Carefully he felt his way up the old, almost obliterated trail rising crookedly beside a small stream.”
The high peak upon which we clung seemed the central core of focus of all the mountains around, and on every side we looked down vertically thousands of feet, deep down into vast, terrible deﬁles, black and ﬁr-clothed, which stretched away until lost in the distance and smoke.
— Fitz Hugh Ludlow, The Heart of the Continent