black belt

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The rank of expert in a martial art such as judo or karate.
• noun The black sash that symbolizes this rank of proficiency.
• noun A person who has attained this rank.
• noun A region of rich, black soil.

from the GNU version of the Collaborative International Dictionary of English.

• noun (Martial arts) a comedy that treats of morbid, tragic, gloomy, or grotesque situations as a major element of the plot.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun The highest belt colour in various martial arts.
• noun Someone who has attained a black belt

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a person who attained the rank of expert in the martial arts (judo or karate)
• noun a black sash worn to show expert standards in the martial arts (judo or karate)