casemate
/ˈkeɪsmeɪt/noun
1- historical a small room in the thickness of the wall of a fortress, with embrasures from which guns or missiles can be fired〈史〉（堡垒中的）暗炮台。
1.1
- an armoured enclosure for guns on a warship军舰炮塔。
词源
mid 16th cent.: from French, from Italian casamatta, perhaps from Greek khasma, khasmat- （see CHASM）.