noun (n)

• absentminded dreaming while awake(noun.cognition)

  Synonym:
  air castle, castle in spain, castle in the air, daydream, daydreaming, oneirism, revery
  

  source: wordnet30
• an abstracted state of absorption(noun.cognition)

  Synonym:
  revery
  

  source: wordnet30
• A loose or irregular train of thought occurring in musing or mediation; deep musing; daydream.(noun)

  source: webster1913