fortress

Từ điển Oxford Advanced Learner 8th

fort·ress [fortress fortresses] BrE [ˈfɔːtrəs] NAmE [ˈfɔːrtrəs] noun
a building or place that has been made stronger and protected against attack
•a fortress town enclosed by four miles of ramparts
•Fear of terrorist attack has turned the conference centre into a fortress.

Word Origin:
Middle English: from Old French forteresse ‘strong place’, based on Latin fortis ‘strong’.

Example Bank:
•The fortress fell after a nine-day siege.
•They took refuge in the fortress.
•The medieval fortress town is enclosed by four miles of ramparts.