An abîme is the geographical term for a vertical shaft in karst terrain that may be very deep and usually opens into a network of subterranean passages.

A pit cave, or vertical cave — or often simply called a pit (in the US) or pot (in the UK) — is a type of natural cave which contains one or more significant vertical shafts rather than being predominantly a conventional horizontal cave passage. Pit caves typically form in limestone as a result of long-term erosion by water. They can be open to the surface or found deep within horizontal caves. Among cavers, a pit is generally defined as a vertical drop of any depth that cannot be negotiated safely without the use of ropes or ladders.