Ad-seg is short for Administrative Segregation. This is the SHU or the hole as some call it. This is maximum security, usualy solitary confinement incarceration. It is a very structured environment with very little time outside the cell. There are two reasons for being sent to the SHU, Administrative or Disciplinary. Administrative could be simply having the inmate stay there awaiting a bed. Another reason is that there is a threat on the compound to this inmate and the short term solution is to separte them from the problem. Administrative can also be where the inmate asks to be placed in "protective custody" or PC - where the inmate notes a threat and the only way to remain safe is to "check in" to Ad-seg.