When your partner tends to do unholy sexual things during intercourse; rough/ nasty sex; such as choking, hair pulling, throwing your body into positions, kinks, anything else that you can think of that would get you aroused.
A person pretending to be something they aren't, or an impostor. This is inferred because of the old alien movies where alien pods appear on earth and the "pod people" dispose of the humans and slowly reproduce the bodies, pretending to be humans.
The pod person was pretending to be my father, but I knew that he was an alien when he acted differently than my father ever would have.