What does the term 'crown jewel' stand for, as a defence strategy in respect of a takeover bid?

In business, when a company is threatened with a takeover, the 'crown jewel' defence is a strategy in which the target company sells off its most attractive assets to a friendly third party or spins off the valuable assets into a separate entity. Consequently, the unfriendly bidder is less attracted to the company's assets. Other effects of this strategy include dilution of holdings of the acquirer, making the takeover uneconomical to third parties, and adverse influence on current share prices. The way of implementing this type of strategy by the target company is to sell its 'Crown Jewels' to another friendly company (often referred to as a 'White Knight'). Later, when and if the acquiring company withdraws its offer, the target company can buy back the assets sold to the 'White Knight' at a fixed price agreed in advance.