A Jam Up is something that one person does/says/acts out/implies that will make another feel foolish/stupid/angry/lame or all of the above. A Jam Up is most effective when done before a co-worker, boss, friend or foe. It's possible to be done in private. Jam Ups are rated. Code 4 being a major jam up, and Code 1 being borderline. A Jam Up is best illustrated through the photo of Chauncey Billups jamming up Derek Fisher in the NBA Finals.