A rare coup whereby a seemingly certain trump loser vanishes.
For example:
Hearts are trumps, and South, declarer, leads the ♠9 from dummy. East ruffs and South will overruff. If East ruffs with the ♥J, South ruffs with the ♥A, and finesses the ♥10. If East trumps with a lower card, South ruffs with the ♥9 and takes the top two trumps for the final two tricks.