noun (n)

• (communication theory) a numerical measure of the uncertainty of an outcome(noun.attribute)

  Synonym:
  information, selective information
  

  source: wordnet30
• (thermodynamics) a thermodynamic quantity representing the amount of energy in a system that is no longer available for doing mechanical work(noun.attribute)

  Example:
  Entropy increases as matter and energy in the universe degrade to an ultimate state of inert uniformity.
  

  Synonym:
  randomness, s
  

  source: wordnet30
• A certain property of a body, expressed as a measurable quantity, such that when there is no communication of heat the quantity remains constant, but when heat enters or leaves the body the quantity increases or diminishes. If a small amount, h, of heat enters the body when its temperature is t in the thermodynamic scale the entropy of the body is increased by h &?; t. The entropy is regarded as measured from some standard temperature and pressure. Sometimes called the thermodynamic function.(noun)

  source: webster1913