A play on the dynamics of a typical backyard trampoline (and possibly others), requiring two people... one person jumping, the other person standing near the outer springs, ready to initiate the double bounce at the appropriate moment.
At a certain point in the air (timing is crucial, but relative to the individuals taking part), the person standing off to the side stomps down near the landing area of the trampoline just as the jumper comes in.
The initial stomp and following landing result in more force being applied downward than the jumper is able to initiate on his/her own. When successful, the jumper will be propelled significantly higher than usual.
Yo, let's go to my little cousin's house and goof off on his trampoline. I wanna get double bounced and see if I can get higher than the roof of their house.