the absolute pressure of the ambient atmosphere, varying with weather, altitude, etc.; expressed in millibars (meteorology) or mm Hg or torr (respiratory physiology); at sea level, 1 atmosphere (atm, 760 mm Hg or torr) is equivalent to: 14.69595 lb/in2, 1013.25 millibars, 1013.25 × 106 dynes/cm2, and, in SI units, 101,325 pascals (Pa). SYN: atmospheric pressure.
