When a car hookup is about to go down and someone opens the car looking for someone/something else and is encountered by twonakedpeople about to do the do.
Alex: I was just going to find Mike and I opened his car door to find Jack and Ashley about to do the nasty. I just totally got stick shafted.
When a fellow chap uses his male genital organ to think, rather than his head.
"Look at you John!. She took half of your equitable estate, your kids, and the only thing she gave you is god damn squirrel AIDS, and hepatitis A through Z. Really naive!!! You should stop thinking with your mind-shaft and start using that bigmelon of yours!".
Royal shaft is when you get treated badly or unfairly by someone else. so if anybody says to you "why you giving me the royal shaft" then it is because you made them mad or been a jerk.