Pertaining to, existing in, or consisting of the atmosphere: as, atmospheric air or vapors.Dependent on the atmosphere.Caused, produced, or operated on by the atmosphere: as, rust is an atmospheric effect.a variety of steam-engine in which the steam is admitted only to the under side of the piston and for the up-stroke, the down-stroke being effected by the pressure of the atmosphere caused by the formation of a vacuum under the piston through the condensation of the steam. This engine, invented by Papin in 1695, was first made a practical success by Newcomen, and was subsequently greatly improved by Watt, through the addition of a separate condenser and air-pump.