Intrinsic ability of an organ to maintain constant normal environment independent of neural and hormonal influences.
It mainly deals with a specific form of homeostasis associated with autoregulation of blood flow despite of changes in perfusion pressure. (By metabolic and myogenic mechanisms)
Most clearly seen in kidney, the heart and the brain. Perfusion of these organs (especially the later two) is essential for life.
Through autoregulation the body can divert blood (and thus oxygen) where it is most needed.