H/t @deagol for stock split description:

Stock price adjusted for any future stock splits. For example, if it splits 2:1 at $180 then quoted prices next day would be $90 but reference price for this market would be x2. Alternatively, I might update the title and resolution criteria to use the post-split price corresponding to the current $200, so would change from $200 to $100 in the 2:1 example (I'd appreciate suggestions in comments regarding these two alternatives, likely most relevant for longer-term markets).