Someone with the highest International Chess Title.

The highest title a chess player can attain (besides World Champion). Awarded by FIDE, it cannot be taken away. Abbr. GM.

The highest title (apart from World Champion) that a chess player can achieve. It is bestowed by FIDE upon players who have achieved certain performance norms. Abbreviation GM. Other titles (in order of importance) are International Master and FIDE Master.