noun (n)

• a particular environment or surrounding influence(noun.state)

  Example:
  There was an atmosphere of excitement.
  

  Synonym:
  ambiance, ambience
  

  source: wordnet30
• a unit of pressure: the pressure that will support a column of mercury 760 mm high at sea level and 0 degrees centigrade(noun.quantity)

  Synonym:
  atm, standard atmosphere, standard pressure
  

  source: wordnet30
• the mass of air surrounding the Earth(noun.location)

  Example:
  There was great heat as the comet entered the atmosphere.
  

  Synonym:
  air
  

  source: wordnet30
• the weather or climate at some place(noun.state)

  Example:
  The atmosphere was thick with fog.
  

  Synonym:
  atmospheric state
  

  source: wordnet30
• the envelope of gases surrounding any celestial body(noun.object)

  source: wordnet30
• a distinctive but intangible quality surrounding a person or thing(noun.attribute)

  Example:
  An atmosphere of defeat pervaded the candidate's headquarters.
  

  Synonym:
  air, aura
  

  source: wordnet30
• The whole mass of aëriform fluid surrounding the earth; -- applied also to the gaseous envelope of any celestial orb, or other body; as, the atmosphere of Mars.(noun)

  source: webster1913