A sex party. Probably like a swingers party, except you don't KNOW that that's what it is until you get there. And, you know, once you get there it's kind of... well... mandatory, to have sex. Because of the mandatoriness of the sex party. And if you don't, then they... you know... rape you. =/
Julie: "This should be fun. I love costume parties."
*walks into party*
Nadab: "Guess what this ACTUALLY is? It's a mandatory sex party, bitch!"
by AhAhChristina December 07, 2010
this is a simple phenomenon, basically just what the words say: it is a party where it is mandatory to have sex -- with allie brosh.

variations have arisen whereby whatever girl or guy that is named becomes (he or she) with whom sex must be had if you want the free drinks and food etc
dave: did you go to the party last night?

dale: i went to the house, but i got there and turns out it was a mandatory sex party and i didn't have any viagara and, you know, i can't naturally get it done with non-asians. allie said just an hour or so of oral would be ok but i was looking around at all the guys who'd already been there a while and had their turn and i kind of thought i'd be better off just going to a movie.
dave: did you go to the karen's mandatory sex party last week?

dale: yeah. it was pretty fun.
by willhard9723 May 19, 2013
A mandatory party in which upon arrival everyone must have sex immediately. Occasionally thrown to as a pre-test to the completion of a Sex Education course.
Bob: Hey Kelly it's nearly the end of the semester! Are you going to the Mandatory Sex Party tonight.
Kelly: Well it IS required for a passing grade.
Bob: Sweet! I'll definitely see you there. *creepy wink*
by Terry Burnettersumthing August 25, 2010
A party where all of the attendees get laid/are offered/arranged a sexual intercourse.

Preferably known in advance and with a voluntary commitment to copulate if necessary on the basis of compulsory empathy
Sure world needs more mandatory sex partying. All those odd fish fucking each others brain out
by ulzha February 05, 2010
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