atmo noun2 •(old-fashioned) 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.In this case, at a pressure of one atmo, the quantity of gas absorbed by one gramme of water is .875 gramme at 0°C. — 1891 •(informal) Clipping of atmosphere formsatmos
