1. Any gas surrounding a given body; a gaseous medium. 2. A unit of air pressure equal to 101.325 kPa. SEE ALSO: standard a., torr. [atmo- + G. sphaira, sphere]
- a. absolute (ata) a unit of absolute pressure (also known as barometric pressure) expressed in atm.
- ICAO standard a. the standard a. adopted by the International Civil Aviation Organization, used for calibrating altimeters and for expressing hypobaric chamber pressures in terms of equivalent altitude; it ignores many deviations found in nature.
- standard a. (atm) 1. the pressure of the a. at mean sea level at 273.15 K, equivalent to 1,013,250 dynes/cm2 or 101,325 Pa (N/m2 in the SI system); 2. a standardized expression of the relation of barometric pressure, temperature, and other atmospheric variables as a function of altitude above sea level.
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at·mo·sphere 'at-mə-.sfi(ə)r n
1) the whole mass of air surrounding the earth
2) the air of a locality
3) a unit of pressure equal to the pressure of the air at sea level or to 101,325 pascals or to approximately 14.7 pounds per square inch
at·mo·spher·ic .at-mə-'sfi(ə)r-ik, -'sfer- adj
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at·mos·phere (atґməs-fēr) [atmo- + sphere] 1. the entire gaseous envelope surrounding the earth and subject to the earth's gravitational field. 2. the air or climate in a particular place. 3. a unit of pressure, being that exerted by the earth's atmosphere at sea level; equal to 1.01325 Ч 105 pascals (approximately 760 mm Hg). Abbreviated atm. atmospheric adjMedical dictionary. 2011.