When someone farts on or near your balls/vagina and the resulting movement of air tickles your balls / vagina.
" Yeah it was crazy. I was big spoon,she was little spoon and passed out. And I was falling asleep but then she fart tickled me and I couldn't help but be aroused. Is that weird?"
"Right in the middle of the lapdance she fartickled me! so I took the $20 out of her c-string and stormed out."