A black belt is worn by someone who has reached a very high standard in a sport such as judo or karate.
He holds a black belt in karate.
2. countable noun
You can refer to someone who has a black belt in judo or karate as a black belt.
Murray is a judo black belt.
black belt in British English
noun
1. martial arts
a.
a black belt worn by an instructor or expert competitor in the dan grades, usually from first to fifth dan
b.
a person entitled to wear this
2. the Black Belt
black belt in American English
1.
a black-colored belt or sash awarded to an advanced practitioner in many of the martial arts, as judo or karate: a beginner wears a white belt, and increasing degrees of skill are symbolized by belts of other colors, culminating in the black belt