noun (n)

• formerly used as a treatment to reduce excess blood (one of the four humors of medieval medicine)(noun.act)

  source: wordnet30
• indiscriminate slaughter(noun.act)

  Example:
  Ten days after the bloodletting Hitler gave the action its name.
  

  Synonym:
  battue, bloodbath, bloodshed
  

  source: wordnet30
• The act or process of letting blood or bleeding, as by opening a vein or artery, or by cupping or leeches; -- esp. applied to venesection.(noun)

  source: webster1913