noun (n)

• a speculative scheme that depends on unstable factors that the planner cannot control(noun.cognition)

  Example:
  His proposal was nothing but a house of cards.
  

  Synonym:
  bubble
  

  source: wordnet30
• an unstable construction with playing cards(noun.artifact)

  Synonym:
  card-house, cardcastle, cardhouse
  

  source: wordnet30