Word forms: plural crown jewels1. plural nounThe Crown Jewels are the crown, sceptre, and other precious objects which are used on important official occasions by the King or Queen.
2. countable noun [usually poss NOUN]If you describe something as someone's crown jewel, you mean it is the most important or valuable thing they have.
The company is also willing to sell 20% of its crown jewel, its credit-card business.