Originating in America, a Mannheim Steamroller is a sexual act that presents itself as having German roots. This act can be between a man and a woman or, in some cases, two men. The receiving partner first defecates while neglecting to wipe. After that, the man initiates anal sex, using the fresh poo as lubrication. As the grand finale approaches, the man pulls out and "rolls" his member on the upper lip region, leaving a streak of poo and semen, slightly resembling Hitler's mustache.
Man: during the holiday season, I love to give my girlfriend the gift of Mannheim Steamroller.
Friend: you mean that lame musical group?!?
Man: hell no! I mean THE Mannheim Steamroller - the single greatest sexual act in the whole wide world!