1. defensive structures, such as walls, trenches, or bastions, built to protect a place from attack
Usage: plural form; typically used in military or historical contexts
2. the action or process of strengthening or securing a place against attack
Usage: abstract noun use; less common than sense 1

Examples

• The ancient city's fortifications protected it from invaders for centuries.
• Medieval fortifications included high stone walls and watchtowers.
• The engineers designed new fortifications along the border.
• The castle's fortifications were damaged during the siege.
• Soldiers worked on the fortifications to prepare for the expected attack.
• The fortifications around the port made it one of the most secure harbors in the region.