Definitions of speculation:

• noun:   a hypothesis that has been formed by speculating or conjecturing (usually with little hard evidence)

  Example: "Speculations about the outcome of the election"

• noun:   an investment that is very risky but could yield great profits

  Example: "He knew the stock was a speculation when he bought it"

• noun:   continuous and profound contemplation or musing on a subject or series of subjects of a deep or abstruse nature
• noun:   a message expressing an opinion based on incomplete evidence