EMBRASURE
port, embrasure, porthole
(noun) an opening (in a wall or ship or armored vehicle) for firing through
Source: WordNet® 3.1
Etymology
Noun
embrasure (plural embrasures)
(architecture, military) Any of the indentations between the merlons of a battlement.
The slanting indentation in a wall for a door or window, such that the space is larger on the inside than the outside.
(obsolete) An embrace.
Source: Wiktionary
Em*bra"sure, n. Etym: [See Embrace.]
Definition: An embrace. [Obs.] "Our locked embrasures."" Shak.
Em*bra"sure (277), n. Etym: [F., fr. embraser, perh. equiv. to
ébraser to widen an opening; of unknown origin.]
1. (Arch.)
Definition: A splay of a door or window.
Apart, in the twilight gloom of a window's embrasure, Sat the lovers.
Longfellow.
2. (Fort.)
Definition: An aperture with slant sides in a wall or parapet, through
which cannon are pointed and discharged; a crenelle. See Illust. of
Casemate.
Source: Webster’s Unabridged Dictionary 1913 Edition