The act of holding a door open for someone approaching but not super close, thus causing the person to guiltily rush to the door. It's not necessarily an act of kindness, but perhaps an act of selfishness, as a doordick attempts to redeem him(her)self by the precariously selfless act.
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.