brilliancy

brilliant +‎ -cy or brilliance +‎ -y

brilliancy (countable and uncountable, plural brilliancies)

1. A shining quality; brilliance.
2. An act of being brilliant.

   His brilliancy lay in combining old concepts from far-flung fields into a new idea.

3. (chess) A spectacular and beautiful game of chess, generally featuring sacrificial attacks and unexpected moves.
   • 2015, Michael Hearst, Extraordinary People: A Semi-Comprehensive Guide to Some of the World's Most Fascinating Individuals, Chronicle Books (→ISBN), page 38

     Bobby Fischer, one of the greatest chess players who ever lived, died at the age of sixty-four from kidney failure. He had lived one year for each square on a chessboard. First of all, you should learn the term “brilliancy.” It refers to a game that is played with spectacular strategy and beauty, typically featuring unexpected moves and ingenious ideas. In other words, the game is extraordinary! At age thirteen, Bobby Fischer won a brilliancy against twenty-six-year old Donald Byrne.