(~s)
1.
A ~ is a precious stone used to decorate valuable things that you wear, such as rings or necklaces.
...a golden box containing precious ~s.
N-COUNT
see also crown ~s
2.
If you describe something or someone as a ~, you mean that they are better, more beautiful, or more special than other similar things or than other people.
Walk down Castle Street and admire our little ~ of a cathedral...
= gem
N-COUNT: oft N of n
3.
If you refer to an achievement or thing as the ~ in someone’s crown, you mean that it is considered to be their greatest achievement or the thing they can be most proud of.
His achievement is astonishing and this book is the ~ in his crown.
PHRASE: usu v-link PHR