noun (n)

• the sound made by something moving rapidly or by steam coming out of a small aperture(noun.event)

  Synonym:
  whistle
  

  source: wordnet30
• the act of whistling a tune(noun.act)

  Example:
  His cheerful whistling indicated that he enjoyed his work.
  

  source: wordnet30
• the act of signalling (e.g., summoning) by whistling or blowing a whistle(noun.communication)

  source: wordnet30