em·bra·sure 
(ĕm-brāzhər)
(ĕm-brāzhər)n.
1. An opening in a thick wall for a door or window, especially one with sides angled so that the opening is larger on the inside of the wall than on the outside.
2. A flared opening for a gun in a wall or parapet.
[French, from embraser, to widen an opening.]
em·brasured adj.
embrasure