An autoclave is a piece of medical equipment that's used to sterilize tools and instruments. After a dentist examines your teeth, she'll put her dental tools in an autoclave to clean them for the next patient.
An autoclave uses high pressure and extremely hot steam to sterilize instruments. It's a vital piece of equipment in a hospital or a lab, since autoclaves make it easy to ensure that medical tools are completely clean and sterile. In French, autoclave means "self-locking," from auto-, "self, and the Latin clavis, "key."