When you haven't washed your hands since you last had a wank and have now found yourself shaking hands with somebody important.
Dave shook hands with his girlfriends father. He remembered how he hadn't washed his hands since having a wank and awkwardly made eye contact with him. It was a Wankshake!
The term "Wankstagangsta" refers to an individual which jerks off once or a large number of times who will then brag about it, typically making it known to as many people as possible.
"Look at him telling everyone, he must think he is cool for being a wankstagangsta" Katy said, making a smug look.