speculation, conjecture -- (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")
speculation, venture -- (an investment that is very risky but could yield great profits; "he knew the stock was a speculation when he bought it")
meditation, speculation -- (continuous and profound contemplation or musing on a subject or series of subjects of a deep or abstruse nature; "the habit of meditation is the basis for all real knowledge")