gunport; embrasure; muzzle
Refers to an opening in a fortification or ship's side through which a cannon is fired, or the muzzle end of a gun. A technical military term.
A cannon was peeking out from the gunport in the castle wall.
Several gunports lined the side of the battleship.
Compound of 砲 (cannon) and 門 (gate, opening). The exact historical derivation is uncertain, but the spelling is conventionally associated with the meaning of a cannon port.