A hyperstition is a self-fulfilling belief.
From Give Up Seventy Percent of the Way Through the Hyperstitious Slur Cascade by Scott Alexander:
A hyperstition is a belief which becomes true if people believe it’s true. For example, “Dogecoin is a great short-term investment and you need to buy it right now!” is true if everyone believes it is true; lots of people will buy Dogecoin and it will go way up. “The bank is collapsing and you need to get your money out right away” is likewise true; if everyone believes it, there will be a run on the bank.
The word "hyperstition" can either apply to a collective hyperstition, like the above, or personal hyperstition, like "This pill will relieve my pain".
A hyperstition that is a prediction is a self-fulfilling prophecy.
In doxastic modal logic, the statement "P is a hyperstition" is written as □P→P. Modal reasoners that satisfy Löb's Theorem believe all personal hyperstitions. This can cause some problems for modal embedded agents. Löbian cooperation works by making mutual cooperation a collective hyperstition.