1. a large, strong building or group of buildings that can be defended against attack
2. a place that is strongly defended or difficult to attack
Usage: figurative

Examples

• The medieval fortress stood on top of the hill overlooking the valley.
• Enemy troops surrounded the fortress but could not break through its walls.
• The ancient fortress had thick stone walls and a deep moat for protection.
• The mountain fortress was considered impregnable by military experts.
• Their home became a fortress of privacy away from the media.
• The company’s headquarters was like a fortress against corporate takeovers.