vault toilet

Short definition from Wiktionary

Noun

1. 1
   A facility for accepting human waste, typically through personal use via urination and defecation, where the waste is directed into an extractable vault tank below the access port used by the person needing facilities. When reaching capacity, the vault is removed from underground and moved to a region with a sewage processing system, where it is emptied, to be reimplanted later. Vault toilets typi