Flèche (fortification)

A flèche (Fr. for "arrow") is an outwork consisting of two converging faces with a parapet and an open gorge, forming an arrowhead shape facing the enemy.

The flèche is similar in plan to other defensive works like the ravelin and demi-lune, but smaller and built in front of the glacis. It was thus part of the outworks of a fortress. It was usually placed in front of the point of a bastion in order to create an additional level of fire.

...
Wikipedia