Punning French reference (appeared in one French movie, I forget which) to rubbishy food, especially oversold rubbishy food. A poubelle is a rubbish bin. Hence poubelle cuisine as opposed to nouvelle cuisine, geddit?
There, and we take the scrapings from the bin liner, mix it in with a few tabs of stalebutter, microwave it for five minutes and they won't know the difference. Voila, poubelle cuisine.
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.