overpressure
/ˌəʊvəˈprɛʃə/noun
1Specifically. Fluid or gas pressure in excess of that which is normal or allowed for; an instance of this.
2 Physics. The difference between the (highest) instantaneous pressure at a point subjected to a shock wave and the ambient atmospheric pressure.
Origin
Mid 17th century (in an earlier sense). From over- + pressure.