Static pressure is defined as the pressure of a fluid that is independent of kinetic energy . Pressure exerted by a gas at rest, or pressure measured when the relative velocity between a moving stream and a pressure measuring device is zero.
Sounds confusing? What it means is when the process fluid is "static" the pressure measured at that point is the static pressure. When fluid is in motion however the meaning is less clear. Lets look at an example of a vessel in which the fluid is in motion. If a tapping point (the measuring instrument point of entry) is installed into the vessel at a low level, the static pressure is the pressure indicated at the instrument.
This term is used in the measurement of level by pressure techniques.