In East Asian martial arts, the black belt is a way to describe a graduate of a field where a practitioner's level is often marked by the color of the belt. The black belt is commonly the highest belt color used and denotes a degree of competence. It is often associated with a teaching grade though frequently not the highest grade or the "expert" of public perception.
Below is a prank video made, a Karate black belt artist pretending to be a white belt and practicing with the members. Enjoy!!