noun (n)

• a serious (sometimes fatal) infection of rodents caused by Yersinia pestis and accidentally transmitted to humans by the bite of a flea that has bitten an infected animal(noun.state)

  Synonym:
  pest, pestis, plague
  

  source: wordnet30
• any epidemic disease with a high death rate(noun.state)

  Synonym:
  pest, plague
  

  source: wordnet30
• a pernicious and malign influence that is hard to get rid of(noun.cognition)

  Example:
  Racism is a pestilence at the heart of the nation.
  

  Synonym:
  canker
  

  source: wordnet30
• Specifically, the disease known as the plague; hence, any contagious or infectious epidemic disease that is virulent and devastating.(noun)

  source: webster1913