intruder
n. 闯入者,侵入者;不速之客
复数 intruders
例句
A fortress is easier to protect because it's simpler: it has no windows, few doors, no skylights, or vent systems through which an intruder might sneak.
堡垒的保护更容易因为它构造更简单:它没有窗口、几乎没有几道门,没有天窗或通风系统这些入侵者可能利用的东西。