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 calthrops across the battlefield to slow down enemy cavalry.
• The invading army deployed calthrops at the gates to prevent a rapid assault.
• Calthrops were used in ancient warfare to create obstacles for advancing troops.
• The garden was overrun with calthrops, making it painful to walk barefoot.
• Police sometimes use modern versions of calthrops called spike strips to stop fleeing vehicles.
• The spiky calthrops plants spread across the dry landscape.
• Hikers in the desert region had to watch out for calthrops that could puncture their boots.