1.a message expressing an opinion based on incomplete evidence
2.a hypothesis that has been formed by speculating or conjecturing (usually with little hard evidence);
speculations about the outcome of the election
3.an investment that is very risky but could yield great profits;
he knew the stock was a speculation when he bought it
4.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