It's when I person wanting to show great disgust towards another person by givng the good old drystroker, by administering the traditional flipping of the bird, but adding the flair of jerking off the finger. To be used in only extreme situations.
Sally: 'That cunt on her cell phone just cut me off!!!!'
Josh: 'She deserves the drystroker!' *Josh then hangs out the window giving 'cunt on her cell phone' the drystroker*