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"
a hypothesis that has been formed by speculating or conjecturing (usually with little hard evidence); "speculations about the outcome of the election"; "he dismissed it as mere conjecture"
an investment that is very risky but could yield great profits; "he knew the stock was a speculation when he bought it"