Overpressure is a pressure difference, relative to a normal pressure, in various circumstances: In engineering, the pressure difference over the wall thickness of a pressure vessel In geology, geologic overpressure, the primary cause of oil gushers In autoclave terminology, process pressure above standard given on a pressure/temperature table
Military science Overpressure or blast overpressure, the pressure caused by a shock wave over and above normal atmospheric pressure Overpressure ammunition, small arms ammunition loaded with a powder charge to produce a greater internal pressure than is standard Overpressure (CBRN protection), a method to create a safe toxin free area against airborne contaminants