1. When you fart and it follows you.
2. When you fart, then intentionally 'drag' the fart past them them.
A play on words, referencing both the mighty stench of a dragon and the dragging motion involved when trying to escape your own stench or when subjecting someone else to your delectable odour.
1.
Person 1: "Holy crap, what is that smell?"
Person 2: "Sorry about that, I farted before I got in the car. It must have been a Dragon Tail."
2.
Person 1: "Holy crap, what is that smell?"
Person 2: *look of victory* "I just totally dragon-tailed you!"
Person 1: "You dick!"