When one is using the facilities and is suddenly overcome by a rancid wafting stench. This stench occurs when gasious build-up from a rotten crotch is let free without warning, so said crotches owner can take a piss... or worse.
The larger the pants (the largest referred to as tent pants) and accompaning crotch, the more overwhelming the odor. Can cause sudden, convulsive vomiting, unconciousness, and in the worst cast scenario, death.
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.