marked by or capable of arousing controversy; "the issue of the death penalty is highly controversial"; "Rushdie's controversial book"; "a controversial decision on affirmative action"
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"