\ ˈkōəˌnu̇(ə)r\
plural koh-i-noors
Definition of koh-i-noor
: something that is or is felt to be the best of its kind
especially
: a usually large and valuable diamond
a young Spaniard with a Koh-i-noor of a diamond on his finger and pearls the size of camphor balls in his shirt front — W. J. Locke