When a bosom is jiggled in just the right way to make tassels on pasties (and presumably the individual boobs they are mounted on) rotate in opposite directions, ie clockwise for the left and counter-clockwise for the right.

As best demonstrated in the peeler bar segment of the movie The Graduate. This can be considered a move practiced only by bad girls, especially when it is executed in such a manner as to percussively drum on the head of an innocent bystander.