Well...it could be short for a shakedown...you know where they do a 'Terry Frisk' for weapons and see how the person reacts (runs, gets unusually nervous, etc.).
OR
If community policing is a big deal where you are, it could be short for a 'shake and talk', which is when the police approach citizens, shake thier hands, introduce themselves and engage in conversation. This activity is a pleaseant way of accomplishing the same thing as a shakedown, because more times than not, if a dude is holding narcotics or guns, they wont talk to the officer or if they do, will either do, say or act in a way that will generate a reasonable suspicion that will allow the officer to change into a more investigative mode.
Now, from being many miles away from your part of the country, these are just educated guesses on my part, based on how things are done over here.
Jim