In the card game of contract bridge, to duck (or ducking) means to play low to a trick to which one has led, losing it intentionally in order to set up a suit or to preserve a control or entry. While mechanically identical, a duck is a manoeuver in one's own suit, while a hold up is in a suit played by the opponents. Nevertheless the terms are used interchangeably with duck or ducking more common.
|A K 4 3 2|
|9 8||W N↑ S↓ E||Q J 10|
|7 6 5|
There are no side entries to the South hand. North is on lead and if he plays to the ace and then king and another, East will win the third trick. The remaining two small cards are good, but there is no way to get to them.
Proper procedure is to duck the first (or second) trick. Then, when the lead is regained, playing the ace and king (or the remaining one of them if the first trick was taken and the second ducked) will establish the suit and the remainder of the suit can be cashed.
Note that defenders can benefit by a hold up play. North, as a defender with (A K 4 3 2) and no outside entries, may do well to hold up on the first or second round of the suit, especially in a notrump contract.