noun (n)

• a disorder of digestive function characterized by discomfort or heartburn or nausea(noun.state)

  Synonym:
  dyspepsia, stomach upset, upset stomach
  

  source: wordnet30
• Lack of proper digestive action; a failure of the normal changes which food should undergo in the alimentary canal; dyspepsia; incomplete or difficult digestion.(noun)

  source: webster1913