Death wobble is a term used predominantly by Jeep and specifically Wrangler owners to describe a violent steering wheel oscillation, typically caused by hitting some form of bump or pothole at higher speeds. For it to occur, there has to be something loose or damaged within the front steering or suspension system. The death wobble gets its name, because the vibrations through the steering wheel are far more frightening than any kind of a wheel imbalance problem. However, using the word "death" would be a misnomer as well, because there are no reported deaths due to the issue over decades of Jeeps experiencing the issue.
A little over a month ago, FCA decided it needed to recall 18,000 JL Wranglers because of a faulty weld around where the track bar is welded to the frame. As of now, there's no evidence linking this faulty weld with death wobble (an FCA spokesperson told us as much), but one of the most common causes of death wobble is a track bar issue. If a bad track bar weld is your problem, you're in far worse shape than any death wobble, because you'll end up with a complete loss of steering.
We asked Jeep about death wobble and a company spokesperson said that it "is not a widespread condition, nor is it a safety issue." FCA also said most of the incidents are linked to poorly installed suspension modifications, such as a lift-kit. However, the most current complaints for JL Wranglers describe unmodified and recently purchased vehicles. This means some vehicles still experience the issue despite being stock Wranglers.
For now, if you experience the death wobble in your new Jeep, it's best to slow down immediately in a safe place. Most are taken by surprise by the sudden oscillations from the wheel, but you should still be able to control the car. FCA says that even if you do experience the issue, it is routinely corrected on its own. We'll keep tabs on this, and update if there are any developments.