The coup is a trump reducing play, the virtual discard of a trump by the declarer, because he has too many. This sound rather odd.

The only thing that distinguished a grand coup from its humbler brother, the coup, is that in the reducing play it is winners instead of losers that are ruffed.

Let us illustrate a grand coup, where South had to get rid of three superfluous trumps, in order to make his contract of 6:

 A Q 7
 K 3
 K Q 4
 A Q 9 6 2
 J 9 8 2
 —
 A 10 8 7 3 2
 J 10 5
 10 4 3
 Q 9 8 6
 J 9 5
 7 4 3
 K 6 5
 A J 10 7 5 4 2
 6
 K 8

Contract: 6 by South

Lead: A

The A followed by the 2. At trick two South ruffs his good diamond. This play would be automatic with a first class player in this situation. Now a heart to the King reveals the position, the declarer has still two trumps too many.

A heart is lead and the 10 finessed. Dummy is re-entered with the Q, and the King of diamonds is lead and ruffed. This is followed by the K, and small to the Q, now the A is ruffed with the seven of trumps, leaving this position:

 A 7


 9 6
 J 9 8
 —
 10
 10 4
 Q 9

 K 6
 A J

Dummy is entered with the A and a good club is played. If East discards, so does South.

By ferlema