The zombie-process has zero watchers and 36 questions in 11 years. Yesterday a new tag defunct was created for defunct processes (no watchers). I don't see what value these tags add if nobody's watching them and they have so few questions asked each year. Since nobody's watching them, their only utility is in searching, and even then the terms aren't common enough that simple text searches couldn't serve the same purpose.
And even if we do need a tag for defunct processes, should it be defunct-process instead, similar to the one for zombie processes?