An illegal underground sex move where a man approaches a female in a group of friends, generally at a bar. After failing to hook up, the man walks away, then waits for her to be separated from her party. Once alone, he proceeds to knock her out and have his way. Once finished, he quietly returns her to the bar, so she wakes up seamlessly to her friends, as though nothing happened.
That hot chick totally blew me off, so I gave her the butterfly effect.