At this time of the year, walking across campus, one cannot fail to notice acorns all over the grounds.
Quite impressing this amount of acorns that an oak can produce...
Looking at those acorns, one might ask: Are you Dead or are you Alive?
(incidentally, in my younger years I was at a Busters concert ... lang ist's her... and that song was one of the "Earworms" back then)
Of course the question could be considered a category error: An acorn is not literally alive (nor really dead), but has the "potential of life". Well, well, greetings from Wittgenstein ("Die Philosophie ist ein Kampf gegen die Verhexung unseres Verstandes durch die Mittel unserer Sprache.")
But seeds are not the only "undead" things -- some animals are really good at hitting the "pause button". Check out this fellow, the Tardigrad. If you can read German, the following is a more detailed description of this Bärtierchen.
Meanwhile, what about the original question? It still keeps people busy, trying to define it...