The exclamation you make when imaging the noise your hand would make on the snare-drum tight ass of a hottie-McHot-Hot girl in spray on leather jeans when you slap her playfully on the backside, knowing that she will truly enjoy and appreciate the gesture, as she turns to link arms with you before bearing you many strong and fine sons. If it this does happen to you then you are living in the Matrix and have discovered that some rules can be bent; others can be broken. Usually it will result in one's nose being bent, sometimes broken.
Dude #1: "Whoa! Look at the arse on that! Don't try to stop me!"
Thrawhapo (sound of hand on leather).
Dude #2: "Here. Have my handkerchief. It will help staunch the bleeding from your nose dude!"