Hey Sparkman,
Brain Dead is when the doctors can not detect any electrical impulses in the brain (e.g. gunshot to the head, suffocation, inoperable brain tumor) – but through machines, they keep the body “alive”. (Done for transplants.)
Death, by any other means (e.g. drowning, car crash, terminal disease) the body may not be able to function even though the brain seems to function fine. The brain is trying to send signals to the organs, but the organs are damaged to the point that they can’t respond. This is why those rich bastards have their heads frozen in hopes that in the future mankind can either transplant the head or create a new body for the brain.
Hope this helps,
James in San Diego
P.S. I meant to add, that in the case of some severe strokes, the brain will be dead but the body works fine!