What is "steam digester"

n. An early kind of autoclave.

The steam digester (or bone digester, and also known as Papin’s digester) is a high-pressure cooker invented by French physicist Denis Papin in 1679. It is a device for extracting fats from bones in a high-pressure steam environment, which also renders them brittle enough to be easily ground into bone meal. It is the forerunner of the autoclave and the domestic pressure cooker.

The steam-release valve, which was invented for Papin's digester following various explosions of the earlier models, inspired the development of the piston-and-cylinder steam engine.