An euphemism to the word "stupid". Since the s-word is considered offensive, it is used as an alternative to avoid any prohibitions.
Caleb: Adam, you're so stupid!
Ms Robinson: Caleb, mind your own language, please.
Caleb: Adam, you're so Ezzanie Jasny!
(Ms Robinson did not care about Caleb)
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.