grand master

WordReference Random House Unabridged Dictionary of American English © 2025

grand′ mas′ter, 

1. Chess International Grand Master. 
2. a person at the highest level of ability or achievement in any field.

Also, grand′mas′ter. 
Grand′ Mas′ter, n. 

1. the head of a military order of knighthood, a lodge, fraternal order, or the like.

grand′ mas′ter, 

1. Chess a chess player in the highest class of ability.
2. a person at the highest level of ability or achievement in any field.

Also, grand′mas′ter. 

Collins Concise English Dictionary © HarperCollins Publishers::

Grand Master noun

1. the title borne by the head of any of various societies, orders, and other organizations, such as the Templars or Freemasons, or the various martial arts