Beat Destruction" - the term I use to describe a type of mashing that involves taking an instrumental and putting a shitload of other instrumentals over it.
The beat I destroyed for this one was Eminem's "Lose Yourself".

Other beats (in case you're not looking at the video):
Mike Jones - Still Tippin
Mob Deep - Shook Ones
Notorious B.I.G. - Dead Wrong
Jay-Z - Moment Of Clarity
Crime Mob - Knuck If You Buck
Kanye West - Drive Slow
Jay-Z - Dead Presidents
Eminem - Till I Collapse
Dr. Dre - Nuthin But A G Thang
The instrumental for Lose Yourself plays throughout the entire mix