Many hunting weapons are made of meta and have sharp twisted ends called barbs. The weapon is designed so that the front piece penetrates the skin of the animal and the barbs then prevent it from being easily pulled out. The weapon often has a piece or rope attached yo 'reel in' the prey. This sort of weapon is especially useful when an animal is fast and might otherwise find it easy to escape by running or swimming away. Some fish hooks are barbed, as are whale harpoons, and old fashioned arrow.
We can buy barbed wire fence to enclose a field and prevent farm animals escaping. Barbed wire is also often used at the tops of walls to prevent people getting in or out of an area.