1. a spiked metal device with four points, designed so that one point always faces upward, historically scattered on the ground to injure the feet of enemies or puncture tires
Usage: also called caltrops (plural); historical military weapon
2. any of various plants with spiny seed pods or fruits, especially those of the genus Tribulus
Usage: botanical sense

Examples

• Medieval soldiers scattered caltrops across the battlefield to slow down the enemy cavalry.
• The road was littered with caltrops that punctured the tires of passing vehicles.
• Caltrops were used in ancient warfare to create defensive barriers.
• The caltrop plant grows in arid regions and produces painful spines.
• Police used caltrops to stop the fleeing suspect's car.
• Caltrops remain an effective anti-vehicle obstacle in modern military applications.