Here’s a challenging bidding term you may not have heard before.

It’s called “unusual over unusual.” Sitting North, with South dealing and no one vulnerable, you hold:

            ♠️ K 4 3 2
            ♥️ A 2
            ♦️ A Q 10 5 4
            ♣️ J 10

South opens 1♦️ and West overcalls 2NT. That’s the “unusual 2NT” promising 5-5 in the two lowest unbid suits, in this case clubs and hearts. These two-suited overcalls, usually with sub-opening values, are the bane of opponents.

Here are your options:
• Pass.
• Double, showing strength in West’s hearts or clubs, with the possibility of later doubling for penalty.
• Bid the lower of the two suits in the 2NT overcall, in this case 3♣️, to show enthusiastic support for partner’s diamonds and game-going values.
• Bid the higher of the two overcalled suits, 3♥️ here, to show strength in the unmentioned suit. That would be spades in this auction. You have at least five of them and invitational values.
• Raise partner’s diamonds at the three level, nonforcing.

What would you bid with the hand above?

First, appreciate the trouble West has put you through by bidding 2NT. Interference bidding will do that. You and partner have opening hands; you should be in game. But how to get there?

A lot of North-South partnerships will go to ground on the shoals.

Fortunately, you’ve got “unusual over unusual.” It got that name because you may be cuebiding an opponent’s suit over the unusual 2NT.

After consulting the guidelines above, what do you bid?

I would bid 3♣️ to show a good hand and support for partner’s diamonds.

Now let’s change the North hand:

            ♠️ K Q 4 3 2
            ♥️ A 2
            ♦️ A Q 10 5 4
            ♣️ J 

Again, South bid 1♦️ and West overcalled 2NT. Over to you. I wouldn’t want to be in 3NT with such an unbalanced hand. I’d prefer some contract lower than 5♦️. So, here’s a perfect hand to bid 3♥️ showing a holding at least five spades and invitational or better values. 

It would be perfect if partner has 3+ spades and you wound up in 4♠️. If not, you have a diamond fit.
There’s a lot to understand about “unusual over unusual,” and you may struggle at first. I know you will be, in King Lear’s words, the pattern of all patience.