ghost
n.— «The two are known as “ghosts,” in police parlance, or undercover officers whose job is to keep an eye on and provide back-up to a third undercover officer who is doing the buy-and-bust work.» —“Man Shot Dead by Police on Lafayette” The Local (Fort Greene, Brooklyn, New York) July 11, 2009. (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...
Responding to our discussion about thin places, those spots where the boundary between this world and other realities seems narrow or permeable, a listener in Kirkland, Washington, sent us some eloquent thoughts about her own experiences of that...