The act of inserting ones johnson into the vagina,while forcing her onto her back in order to ride her down a staircase, hence the bobsled.
Bob- Dude did you notice those marks on your staircase
Jeffey- Yeah whats up with that?
Bob- Me and your mom tried the slovakian bobsled last night, shit got out of hand
Jeffey- Dammit dude again?