"Body-possession" in the context of a porn video tag refers to scenes where one person is experiencing a state of being possessed or controlled by another, often involving domination and submission themes. This can include actions like taking control of someone's body movements, engaging in forced or extreme sexual acts, or being physically manipulated into various positions against their will. It's a kink or fantasy that some people enjoy in their porn viewing experience and it's usually depicted with heavy BDSM elements