house of cards

Noun	1.	house of cards - a speculative scheme that depends on unstable factors that the planner cannot control; "his proposal was nothing but a house of cards"; "a real estate bubble" Synonyms: bubble
	2.	house of cards - an unstable construction with playing cards; "he built three levels of his cardcastle before it collapsed" Synonyms: card-house, cardcastle, cardhouse

bubble, scheme, strategy