standard pressure
Chosen value of pressure denoted by \(p^{\unicode{x29B5}}\) or \(p^{\,\unicode{x26ac}}\). In 1982 IUPAC recommended the value \(10^{5}\ \text{Pa}\), but prior to 1982 the value \(101\ 325\ \text{Pa}\) (= \(1\ \text{atm}\)) was usually used.
Green Book, 2nd ed., p. 54 [Terms] [Book]
PAC, 1994, 66, 533. (Standard quantities in chemical thermodynamics. Fugacities, activities and equilibrium constants for pure and mixed phases (IUPAC Recommendations 1994)) on page 536 [Terms] [Paper]