turret
/ˈtʌrɪt; `təɪt/ n
1 small tower on top of a larger tower or at the corner of a building or defensive wall 塔楼; 角楼.
2 (on a ship, an aircraft, a fort or a tank) low flat (often revolving) steel structure where the guns are fixed and which protects the gunners （舰船、 飞机、 要塞或坦克上的）炮塔（通常可旋转）
a warship armed with twin turrets 装备著双炮塔的战舰.