i don't speak italian very well and the version of the film i watched had no subtitles. i understood most of the film, except when they would put their thumbs to their nose and say something that sounds like "piti pi!" anyone who's seen the film can fill me in?
---- My answer:
It's a game between Carlina and Levante. She would like to be the girlfiend of Levante, and tries to have a "love gesture" between them, a kind of private sign of agreement. It's not a common use; in real life, nobody has a "love gesture". It's an invention of that foolish character.
Generally, it's a children gesture; the ordinary meaning is "ti prendo in giro" (I'm poking fun at you), and is not joined to "piti pi".