A unit of pressure sufficient to support a 1-mm column of mercury at 0°C against the standard acceleration of gravity at 45° north latitude (980.621 cm/s2); equivalent to 1333.224 dynes/cm2, 1.333224 millibars, 1.35951 cm of H2O, 133.3224 newtons/m2 (or Pa); 1 atmosphere (atm) equals 760 Torr. [Evangelista Torricelli]
