- noun a unit of pressure defined as the pressure that will support a 760 mm column of mercury at 0°C at sea level, equal to 1.01325 x 105 newtons per square metre
- A pressure equal to 14.7 lb per sq in (1.01 x 10 dynes per sq cm).
- A unit of pressure intended to equal the pressure of the earth's atmosphere at sea level. One standard atmosphere equals 101.325 kilopascals, or 760 torr. Also called atmosphere (2).