If it's a party where sex is going to happen, it involves placing funnels in willing guys' asses (or mouths) and having multiple guys shoot off in them, and/or piss in them. The idea being to fill the recipient with as much of whatever as possible.
If it's not a sex party, then it's about chugging beer from a funnel...usually for bragging rights over who can chug the fastest.
If there's a fraternity involved, it could be a combination of these.
Make sure you know which before you go.
