noun
A belt worn as part of a uniform in martial arts, typically indicating the wearer's rank or level of proficiency
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He has been training for years and finally earned his black belt in karate.
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My friend is a black belt in taekwondo and can kick anyone's butt.
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Watch out for that guy, he's a black belt in jiu-jitsu.
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She is a black belt in negotiation, always getting the best deals.