noun (n)

• a card that is used instead of cash to make telephone calls(noun.possession)

  Synonym:
  phone card
  

  source: wordnet30
• a printed or written greeting that is left to indicate that you have visited(noun.communication)

  Synonym:
  card, visiting card
  

  source: wordnet30
• a distinguishing characteristic or behavior(noun.cognition)

  Example:
  Bombs are a terrorist's calling cards.
  

  source: wordnet30