See, this is just my point. Death is a more gradual and complicated process than we tend to think, so there's no consensus, even medically or scientifically, on what differentiates being dead from being nearly dead.
However, there is such a thing as being "clinically dead." Clinical death
is the cessation of heartbeat and respiration. This used to be considered just plain death, but now it's often reversible with resuscitation techniques, and there have been cases of spontaneous revival. So these days there are at least two medically recognized categories of "dead" -- clinical and permanent. Essentially clinical death is the first stage of the process of death. Death isn't a single instantaneous event the way we used to believe, but a transition that begins with clinical death and progresses to permanent death, unless it can be interrupted and reversed.
's best friend would indeed have been clinically dead. That's an accepted medical term for his condition at the time. He just wasn't irreversibly dead yet.