In various countires with relation to the UK Commonwealth, it's equivalent to giving someone the finger. If you do with a bit of an elbow swing it basically translates to "Shove it up your ass"
> This origin legend states that English archers believed that those who were captured by the French had their index and middle fingers cut off so that they could no longer operate their longbows, and that the V sign was used by uncaptured and victorious archers in a display of defiance against the French.
I guess that's all the keywords needed in order read the original comment fully.
... It must be somewhat awkward to play Rock Paper Scissors among friends. LOL