One of two things which happens when you're playing Quidditch
1. In the middle of intercourse, the male withdraws for a few minutes to perform vigorous oral sex on the female (going down hard and fast...), and then continues intercourse (...and pulling back up).
2. In the middle of any sex act, a female signals to the male that she is ready to catch the snitch
(by moaning, saying "here it comes!", et cetera) before she actually is. This tactic is used to end a Quidditch match early, without hurting the other player's feelings. It's intention is to inspire the male to "follow" the girl, looking for his own Snitch, and ending the match under the assumption that the female did too.
Neither of these is to be confused with the Wronski Defensive Feint, a move performed in the Harry Potter books.
1. Viktor Krum performed the Wronski Feint on Hermione during their tryst on the first night of Easter vacation
2. Jack was a good friend of Sarah's, so she performed the Wronski Feint when Jack wasn't getting her off. They remained friends to this day.