复数:citadels
1.(居高临下的)城寨,城堡,要塞
2.〈比喻〉根据地,大本营;避难所
3.(军舰上的)炮廓
1.a castle intended originally for the defense of a city, usually built on a high place
2.a place that seems to represent all the important aspects of an idea, method, or practice