团城（拼音：tuán chéng）是指在古代，为防御外敌入侵而建造的城市式防御设施。它通常由城墙、城门、护城河等构成，具有坚固的防御能力。

How to pronounce: tuán chéng [t-wan ch-ung]

Usage: 团城 is used to refer to a fortified city or defensive structure built in ancient China.

Example Sentences:

1. 这座团城是由秦始皇统一六国后修建的。

This fortified city was built by Emperor Qin Shihuang after he unified the six states.

2. 为了保护边疆安全，当时的决定修建一座团城。

In order to protect the border, the government at that time decided to build a fortified city.

3. 这座团城曾经经历过多次战争，但始终未被攻破。

This fortified city has gone through many wars, but it has never been breached.

4. 城内居民在团城的保护下过着平静安稳的生活。

The residents inside the fortified city live a peaceful and stable life under its protection.

5. 团城的设计巧妙，使敌人难以攻破。

The design of the fortified city is clever, making it difficult for enemies to breach.

Synonyms and Usage:

1. 城郭 (chéng guō): fortress; used to refer to a fortified city or defensive structure.

2. 城堡 (chéng bǎo): castle; used to refer to a large and fortified building typically built in the Middle Ages for protection against enemies.

3. 城市防御工事 (chéng shì fáng yù gōng shì): city defense works; used to describe the defensive structures and measures taken by a city to protect itself from potential threats.

Editor's Summary:

团城 is a term used in ancient China to describe a fortified city or defensive structure built for protection against enemies. It is commonly seen in historical texts and has a strong cultural significance. Other similar terms such as 城郭 and 城堡 can also be used to refer to fortified cities, but they may have slightly different connotations. Overall, 团城 is an important term in Chinese history and reflects the strategic thinking of ancient Chinese rulers in defending their territories.