An act of masturbation or wanking performed when your family/flatmates are out and you are at home alone, allowing you to knock one out without having to worry about getting caught, and enabling you to view pornography with the volume turned way up.
"Hey man, I'm having a partywank at my place tonight."
A meeting where in a group of people who work in the office come up with a Absolutely stupid idea for something new in the factory, and they all pat each other on the back for coming up with it.
Worker #1: WTF is Jimmy doing?
Worker #2: That's the new machine we got in to improve productivity.
Worker #1: that's not going to work at all, I wonder how the bosses signed off on this.
Worker #2: yeah that meeting must have been a Wankparty.
The act of masturbating (wanking) whilst in a party with your mates, that are in earshot of your moaning through the headset.
I came back and put on my headset and was greeted with vigorous sexual noises coming from a member (Kellah) in the party. Kellah is a blooming party wanker!