This is a sexual position. It takes place in a public restroom stall, usually at a bar, or crowded restaurant. The man tilts the woman in the direction of the toilet bowl. Upon insertion, a thrust and tilt downward will result in the woman's head being inside the toilet. The man then flushes the toilet while continuing sex, giving the woman a swirly. This act continues for as long as required to instill shame into the woman, who must go back out into public with her hair drenched, or until the man in finished.
I saw this chick at the bar come out of the bathroom with soaked hair. She definitely got a Tilt-A-Swirl.