Thong Whistle

The undergarment equivalent of placing a blade of grass in between the palms of your hands ,then blowing and creating a whistling sound. The Back of the thong is nestled directly between the butt cheeks, once air pressure is applied in the form of a fart, the thong reverberates and creates a low whistling sound.

Damn, that girl with the big booty busted out a thong whistle that sounded like a barge coming to shore....