A fictional term created by author Kristin Cashore to define someone who is Graced--that is, he or she has an extreme skill. Someone who is Graced with swimming may be able to swim as efficiently as a fish. A person Graced with fighting skills is much more talented at fighting than the average person, and so on.
A Grace can develop in many different ways, and no two people ever have the same Grace. For example, one person who is Graced with fighting may be an expert sword fighter, and another may be an expert in hand-to-hand combat. Even those can be proken down further. A combat fighter can be someone who is Graced with agility, while another can be Graced with strength, etc.
Graces can also take abstract forms, such as mind reading.
In Cashore's debut novel "Graceling", Gracelings are often feared by those who are not Graced. A Graceling can always be easily identified: each of them has two different colored eyes.
Katsa, a Graceling, is the main character in Kristin Cashore's novel. She is Graced with killing.
Because Prince Po is a Graceling, one of his eyes is gold and the other is silver.