Phrase used to diffrentiate between the act of shaking of the schlong (after urination) as compared to the act of masturbation. The phrase is best illustrated in the military when a drill sergeant barks at a recruit (who is urinating), "more than than three shakes is pleasure and that's not what you're here for.' The original phrase "shaken not stirred" has an obvious root in the James Bond movies, but also serves a different context. In this sense it is often used in contempt.
We were in a hurry, but Frank had to piss first. Damn, but he took forever in the mens room. Mike was getting pissed off and joked that maybe he was beating off. I finally stuck my head in the door and yelled, "LET'S GO! SHAKEN, NOT STIRRED!"