blue light bandit n. a person with criminal intentions who impersonates a police officer in a patrol car. (source: Double-Tongued Dictionary)
Further reading
A firefighter named Steve in Newport News, Virginia, wonders why in his line of work, and for some police, certain additional kinds of days off after long unbroken shifts are called Kelly days, Kelly shifts, or Kelly time. The term most likely comes...
Aaron in Los Angeles, California, notes while using public transit in Britain he and other passengers were instructed to alight from the front, meaning “exit the car from the front.” Alight comes from an Old English word alihtan, literally, to...