Letting out a huge fart while taking a hot shower. The steam intensifies the effect, making it many times worse than normal, basically baking the smell into the walls, shower curtains, and towels.
This is similar to a Dutch Oven, except much, much, worse, and is a reference to a popular method of execution during the Holocaust.
Dude, I was taking a shower with my girlfriend and I totally German Ovened her. The funny thing is, she's Jewish, so it hit her twice as hard.
With connection to the dutch oven, the German oven has a similar principle, yet the main diference is the gas that is released into the 'oven'.
As history tell us the German oven will contain Zyklon B an will therefore kill the fellow occupant of the bed.
A brutal joke with dark consequences, but it is German after all.
Adolf: Come into ze bed my pretty *releases German Oven*
Anne: Okay, mein Fürher
*Anne gets in bed and begins to choke and slowly suffocates while Adolf watches on in admiration*
The mechanics and principles are exactly the same as a Dutch Oven however the act involves following though to lay a fresh poop.
Then one locks the other participant (Preferably the one who did not do the poop) under the sheets.
Person1 "I can't believe you followed through trying to Dutch Oven me."
Person2 "That's how a German Oven works"