1. a tall structure used for keeping watch over an area, especially for military or security purposes

Examples

• The prison watchtower was equipped with searchlights.
• Guards in the watchtower spotted the approaching enemy forces.
• The medieval castle had several watchtowers along its walls.
• From the watchtower, they could see for miles across the valley.
• The border patrol built a new watchtower near the crossing.
• Soldiers took turns manning the watchtower throughout the night.