The German Pole vault is like one of those gross/outrageous sexual things that you always joke around with your friends like the Alaskan Pipeline
but would never actually attempt. The German Pole vault however is not gross, but would generally end in injury (and embarassment).
The German Pole Vault is when your female sex partner is lying on the bed, and the male starts standing on the bed, and then jumps down, aiming his penis into her vagina. This requires practice, accuracy and some luck or else you will end up with a bent penis.
Bro: Dude, she is so hot, I might try the German Pole Vault on her.
Dude: Thats hilarious, but if you miss, you wont have sex ever again.