A method of play by which the hand with longer trumps (declarer) ruffs losers. Dummy’s trumps then draw the remaining trumps.
You are South in a contract of 7♠ and have twelve top tricks. You can get home however, when the suits break evenly, by means of a dummy reversal.
By ruffing dummy’s three losing diamonds with top trumps, you end up with three trump tricks, four club tricks, three tricks from the red suit winners and three tricks by trumping diamonds in hand.