The act of jabbing a person with a sharp object, preferably a pin, and shouting the words 'Pin-Pin!'; preferably in a camp, middle-class accent. If 'Pin-Pin!' is not shouted then THIS DOES NOT COUNT as an act of Pin-Pinning! and should probably be considered assault with a deadly weapon.
Under NO CIRCUMSTANCES should you Pin-Pin:
I am going to pin-pin Noel Fielding next Thursday!
"That purple-nurple really hurt my pin-pins!"