From the glossary of terms used in behavioral ecology, animal behavior, and evolution thanotosis is defined as playing dead; death-feigning behavior.

I guess "playing possum" isn't scientific enough.

Source:
http://www.zoo.ufl.edu/be/pages/glossT_Z.html

Also mentioned in a site about vampire clans:
"Samedi-- "Stiffs or Zombies" Disciplines: Thanotosis, Necromancy, Obfuscate"
members.aol.com/SilasMcbth/index2.html