atmo

from The Century Dictionary.

• noun The first element, meaning vapor, in some compound words of Greek origin.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Physics) The standard atmospheric pressure used in certain physical measurements calculations; conventionally, that pressure under which the barometer stands at 760 millimeters, at a temperature of 0° Centigrade, at the level of the sea, and in the latitude of Paris.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun physics, dated The standard atmospheric pressure used in certain physical measurements and calculations; conventionally, that pressure under which the barometer stands at 760 millimeters, at a temperature of 0° Centigrade, at the level of the sea, and in the latitude of Paris.