Ejaculating onto a female's body or hair and rubbing it in.
Man 1: She is just acting like a real bitch these days.
Man 2: Just giver her the ol' Man Goo Shampoo treatment.
Girl 1: What's wrong with your hair?
Girl 2: My asshole boyfriend came in my hair!
Girl 1: Why the fuck did he do that?
Girl 2: He said it was a "man goo shampoo", and it would make me a stronger person.