spinner
n.— «There’s the predictable “Hi, Mum” and “Missing you, Julie” alongside common prison lingo such as “screw” and “spinner,” the latter a term referring to the inmate generally known as the unit idiot.» —“The House of Gronk” by Lara Zamiatin Sydney Morning Herald (Australia) Oct. 31, 2004. (source: Double-Tongued Dictionary)