Something you say when something bad or surprising happens. The word "quad" takes up the space of any real cuss word. Also saying "What the quad?!?!" infront of emo kids confuses them and causes them to feel even more isolated. Saying it in front of posers will inevitably cause them to start saying it excessively within the next week.
One of your friends: "do you like my Fallout boy T-shirt?"
You: "what the quad!"