On February 28, Elon Musk posted that it was likely Starship would become fully reusable in 2025. You can see the X post here: https://x.com/elonmusk/status/1895598258225106984
This market will resolve to "Yes" if SpaceX or Elon Musk announces that Starship is fully reusable by December 31, 2025, 11:59 PM ET. Otherwise, this market will resolve to "No".
Note, this market refers to the Starship upper stage and does not require reusability for the Super-Heavy booster.
For this market to resolve to "Yes" it is not necessary that an actual reuse occur, only that SpaceX or Elon Musk announces that Starship is fully reusable by this market's resolution date.
The resolution source for this market is announcements by Elon Musk and SpaceX, or their official representatives.