Just launched! Learn slang while watching funny vids: urbandictionary.tv
1. Greenbag
1. Douchebag, male, usually from Wisconsin.

2. Moldy scrotum that results from your girlfriend putting her hand in a bag of shredded parmesan before stroking you mercilessly. (Cheese may or may not be from Wisconsin.)
Don't invite that Greenbag to our superbowl party!

I told him to go wash his Greenbag before he came back to bed.