Flowmex autoclave is a machine that uses steam under pressure to kill harmful bacteria, viruses, fungi, and spores on items that are placed inside a pressure vessel. The items are heated to an appropriate sterilization temperature for a given amount of time an apparatus in which special conditions (such as high or low pressure or temperature) can be established for a variety of applications especially : an apparatus (as for sterilizing) using steam under high pressure. autoclave. verb. autoclaved; autoclaving.