from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. The belief that no pope since the 1960s has been a true pope.
Sorry, no etymologies found.
Although, it seems sedevacantism is something deeply frowned upon in the Society.
I'm no expert on these various strains of crackpottery, but I think there's some potential overlap between Gibson's sedevacantism and Mayan-based apocalypticism.