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→Total pressure
\[ p_0=p+p_D \]
It is the '''static''' pressure that the fluid will reach if it is '''stagnated''', i.e. brought to a rest from motion. If you stick an object into water flow (try this with a finger, be sure not to use hot water), you will observe the water level increase a bit in front of that object, which is a consequence of stagnating the water increasing its pressure, reflected in depth.
There is an extra requirement that the stagnation happens in an isentropic manner, but this is usually true when we consider air at low speeds. In fact, the stagnation of air is usually treated as isentropic unless we know it is not (for example, if we know a shock wave is present). Not being isentropic means mechanical energy is dissipated in the process, if you spill water on the ground and let itself come to a rest, you will not observe the level rise, for example.