noun (n)

• feeling an inappropriate lack of seriousness(noun.feeling)

  Antonym:
  gravity, solemnity
  

  source: wordnet30
• a manner lacking seriousness(noun.attribute)

  source: wordnet30
• The quality of weighing less than something else of equal bulk; relative lightness, especially as shown by rising through, or floating upon, a contiguous substance; buoyancy; -- opposed to gravity.(noun)

  source: webster1913