I've blogged about overselling the description . . . but I think this undersells it:
"Some monsters are immune to poison, either from very slow metabolisms (zombies) or because they live
with it on a daily basis (dragons)."
- Tunnels & Trolls, 5th edition, 1.52.5
"very slow metabolisms"? Sure, that's one way to describe the metabolism of a dead person. It's not how I'd go about it, but yeah, sure, "very slow." Like how "zero" is a "low number."