A woman's breasts. You know, your girlfriends Gozongas. Your mom's Meat Rack. Your daughters Tetangas. Get the idea?
The word comes from the noise that a bicycle horn makes when you squeeze it.
See Peh Peh Milk
Frank - "WHOA! Check out those Peh Peh's!"
Mitch - "Wow, those are quite the pair" *Goes up to women, squeezes her breasts while making "Peh Peh" horn sound*
Frank - "Nice man!"