Is death reversible?

Not if you accept the definition of death i alluded to before: the irreversible deterioration of the bilological system which goes beyond an arbitrary limit.

However it may be possible to change the definition itself. Its possible that we can preserve the biological system, that is the body, and wait for science to evolve to such an extent in the future that the deterioration once believed to be irreversible can be corrected and enough biological functions of the organism may be recovered "bring the person back to life". Efforts are already on as in the cryosuspension programs.

A person who wakes up from un-responsive comatose stage after a head injury or stroke has actually gone close to the arbitary limit which we have set for death and then recovered enough function to become self aware. There may be permanant change to his mental faculties and physical functions as a result of the neurological damage. Yet he continues to "live" and is identified as the same person by his relatives.

All this just goes on to prove that the human brain is just a biological system, a very complex one, that as long as it functions, gives the manifestation of life. If its destroyed, life ends. There is no soul. There is nothing after death.