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: Usually used in plural form; Historical military weapon
2. Any of various plants with spiny seed pods or fruits, especially those of the genus Tribulus.
Usage: Botanical sense; Usually used in plural form

Examples

• Medieval soldiers scattered caltrops across the battlefield to slow down enemy cavalry.
• The road was blocked with caltrops to prevent vehicles from passing through.
• Police used caltrops to stop the fleeing suspect's car.
• Caltrops with their sharp spines can puncture bicycle tires.
• The desert floor was covered with caltrops, a plant with painful seed pods.
• Ancient armies relied on caltrops as an inexpensive but effective defensive weapon.