A person who lives on your couch for free. They don't pay Rent, Eat all your food, Take up all the time on your XBox and Smoke all your weed. They don't move all day, try to get a job or be productive at all.
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.