On its own the phrase is incomplete. The useful numbers are the flowing bottomhole pressure, taken while the well is producing, and a shut-in pressure. A short shut-in is still a buildup. A static reservoir pressure is what that buildup is extrapolated toward, or the average pressure of the drainage volume.
Tubing-head pressure is the surface counterpart. The difference between them is the weight of the fluid column, minus friction when the well is flowing. Once gas breaks out of solution, that column's weight is no longer a simple hydrostatic head, and a bottomhole pressure inferred from the surface gauge carries that uncertainty.