A finesse against a lower honour held by one opponent in preparation for a finesse against a higher honour held by the other opponent.
For example:
If, as South, you have reason to place East with the ♠K, you reject the normal play of leading up to the queen. Instead, you finesse the nine, losing to the jack. When you then get the lead in the North hand, you lead the queen to pick up East’s king and West’s ten.