Taking a shit in the upper bowl of someone's toilet, such that the shit is not moved to the sewer when the toilet is flushed. The result is rotting shit in the top bowl of the toilet.
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.