an unstable construction with playing cards; "he built three levels of his cardcastle before it collapsed"
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"
not sensible about practical matters; unrealistic; "as quixotic as a restoration of medieval knighthood"; "a romantic disregard for money"; "a wild-eyed dream of a world state"