What is Roshombo?
1.
A testing of one's strength. Particularly when two men square off and take turns kicking eachother in the testicles. Traditional rules dictate that the first one to fall down loses, thereby making the man who remains standing the victor. A hint to those participating: it is best to reserve the first turn for yourself.
"Hey, that burger looks pretty good. I'll roshombo you for it - and I'll go first."
2.
as seen on south park. How you play is to kick the other guy in the nuts and then he kicks you in the nuts. the first person to falls down or yell in pain loses. It is a very funny game to watch but it is only fun to participate if you kick first (the kicker) and it isnt that fun if you are the one getting kicked ( kickee) hilarious on South Park
Kenny: Hey cartman want to roshombo for the last chocolate salty ball?
CArtman: fuck no kenny you poor bastard its mine!
Kenny: Roshombo! (kicks cartman in the nuts)
Cartman: you bastard! (kills Kenny)