To do or try something in a sneakly way, to avoid attracting attention or suspicion, or being caught in the act of doing or trying it; without others knowing or being aware of it.
He surreptitiously left the room.
She surreptitiously ran away from her boyrfriend.
They surreptitiously smuggled the goods through.
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.