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.