To eat junk food by placing a similar, but slightly different, piece of junk food on top of it. The eater then proceeds to bite both in one motion, hence completing a full fatbastard.
Damn, did you seeSean fatbastard those two doughnuts? Chocolate and Vanilla frosting for the win!
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.