Plant Defense(s). It's when Plants use methods to ensure their survival from being over eaten by Herbivores. Two of the methods include Chemical Defense(s) and Mechanical Defense(s).
I'm very aware of some Mechanical Defenses, as I ride my motorcycle through the woods and thorns get stuck in my leg. I wear cargo shorts most of the time, so I'm vulnerable to this. It's getting cooler/colder every day outside, so soon I'll have the protection of long pants.