Standard atmospheric pressure
From AMS Glossary
standard atmospheric pressure
That pressure (force per unit area) recorded when the height of a column of mercury is reduced to standard gravity and temperature.
It is the pressure exerted by a column of mercury 760 mm high, of density 13 595.1 kg m-3, subject to a gravitational acceleration of 9.80665 m s-2, and equals 1013.25 hPa. This is a sea level consideration at 45°N latitude.