When two fat people are gettin' it on there's the sound of their fat clapping against one another hence the name fat-clap
Joe:Why you actin' so wierd today jeff?
Jeff:'cause last night it was my parents annerversary and i could hear the fat-clap commin' from their room, it was disturbing.
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.