couloir
A steep gorge along a mountainside.
Those deep, dark slots in a mountain known as couloirs are often the most obvious routes of ascent.
A corridor or passage.
rare
It was a hole, in the fence, a large irregular hole, caused by numberless winds, numberless rains, or by a boar, or by a bull, flying, pursuing, a wild boar, a wild bull, blind with fear, blind with rage, or who knows perhaps with carnal desire, crashing at this point, through the fence, weakened by numberless winds, numberless rains. Through this hole I passed, without hurt, or damage to my pretty uniform, and found myself looking about me, for I had not yet recovered my aplomb, in the couloir.
Where it comes from
Borrowed from French couloir (literally “corridor”).
Adapted from the Wiktionary entry couloir (CC BY-SA 4.0).