When you fuck someone from behind while
simultaneously eating pizza off of their back. Typically pizzabacking involves pizza in a box, but fresh-hot pizza can be applied directly to a recipiant's back if they need to be taught a lesson. To simulate an acid trip, try pizzabacking while watching Hanna Barbera cartoons.
If you don't have a sex partner or pizza available and you still want to simulate an acid trip, try watching Hanna Barbera cartoons.