For someone who is very racist toward the african american race: Someone that teases an african american without the african american knowing a clue of what you are doing in any way. The perfect way to laugh and be racist in public. "pinch your skin" refers to there skin color. But in all it is just for jokes.
A trip to a grocery store, convenience store, or gas station for the sole purpose of buying an excessive amount of junk food and sugary drinks, usually with friends. A chud run often happens late at night and ends with everyone involved hating themselves afterwards.