D-forcing is the act of playing music of the dragonforce variety very loudly at passers buy whilst in a car, in order to gain their attention and also to cause surprise. The idea is to have the music set very loudly but paused, so that when a target (a person at the side of the road) is about next to the car, you can press play and "d-force" them. It is important to know that having the windows down will greatly increase impact. For added effect a shout from the people in the car can be used to gain attention just before the music is played.
In a sentence: "You've been d-forced fool!" and "Whoa! I've been d-forced" or "Lets go d-forcing"