2♦ = Showing at least 5-5 in the majors.
The auction had some points of interest apart from West’s bid showing the majors, helpful information for declarer. South’s pass, followed by 3♦, promised extras: He would have bid at his second turn with fewer values. South also judged that a vulnerable game or slam was more promising than a penalty from 2♥ doubled. After that start, the partnership was forced to game. Control bidding followed, and once South confirmed a club control, North ended the auction by leaping to 6♦.
West led the ♣K. Declarer took this with the ace and led a low trump toward the ace. He was shocked by West’s heart discard. Put yourself in South’s place. How will you make 12 tricks on this deal?
Undaunted by the bad trump break, declarer saw that he could make 12 tricks provided West had exactly five spades headed by the jack.
Declarer won the second trick with the ♦A and continued with the ♦4 to the 3 and 8. He then cashed the king of trumps, followed by the ♠A. Then he led a low spade and, playing with the odds when West followed low, finessed the 10. Declarer continued with the ♠K. East saw that ruffing it would allow the contract to make easily (declarer could overruff, draw trumps and claim 12 tricks). so he threw a heart, and so did declarer. Next came the ♠Q, again eliciting heart discards from East and declarer. The ♥A drew club discards from East and declarer. Declarer ruffed a heart and exited with a club at trick 11. East was reduced to the ♦J 6, while declarer held the ♦Q 10 over him. Declarer made the last two tricks and brought his contract home. The full deal: