Source : Webster's Revised Unabridged Dictionary (1913)

Atmosphere \At"mos*phere\, n. [Gr. ? vapor (akin to Skr.
   [=a]tman breath, soul, G. athem breath) + ? sphere: cf. F.
   atmosph[`e]re. See {Sphere}.]
   1. (Physics)
      (a) The whole mass of a["e]riform fluid surrounding the
          earth; -- applied also to the gaseous envelope of any
          celestial orb, or other body; as, the atmosphere of
          Mars.
      (b) Any gaseous envelope or medium.

                An atmosphere of cold oxygen.     --Miller.

   2. A supposed medium around various bodies; as, electrical
      atmosphere, a medium formerly supposed to surround
      electrical bodies. --Franklin.

   3. The pressure or weight of the air at the sea level, on a
      unit of surface, or about 14.7 Ibs. to the sq. inch.

            Hydrogen was liquefied under a pressure of 650
            atmospheres.                          --Lubbock.

   4. Any surrounding or pervading influence or condition.

            The chillest of social atmospheres.   --Hawthorne.

   5. The portion of air in any locality, or affected by a
      special physical or sanitary condition; as, the atmosphere
      of the room; a moist or noxious atmosphere.

Source : WordNet®

atmosphere
     n 1: a particular environment or surrounding influence; "there
          was an atmosphere of excitement" [syn: {ambiance}, {ambience}]
     2: a unit of pressure: the pressure that will support a column
        of mercury 760 mm high at sea level and 0 degrees
        centigrade [syn: {standard atmosphere}, {atm}, {standard
        pressure}]
     3: the mass of air surrounding the Earth; "there was great heat
        as the comet entered the atmosphere"; "it was exposed to
        the air" [syn: {air}]
     4: the weather or climate at some place; "the atmosphere was
        thick with fog" [syn: {atmospheric state}]
     5: the envelope of gases surrounding any celestial body
     6: a distinctive but intangible quality surrounding a person or
        thing; "an air of mystery"; "the house had a neglected
        air"; "an atmosphere of defeat pervaded the candidate's
        headquarters"; "the place had an aura of romance" [syn: {air},
         {aura}]