Depending on where you live, the term “The Big One” can have a different meaning.
On the West Coast, you’re probably talking about the fear everyone has, and tries to ignore, about a major earthquake along the San Andreas Fault. Some believe it to be inevitable, others claim it's only hypothetical, but either way, Hollywood likes making disaster movies based on the worst-case scenario.
In the Southeast, the term is more commonly used to describe NASCAR races at Talladega Superspeedway. Crashes are pretty common at the track, but what really packs in fans and has them on the edge of their seats is the wait for the wreck that takes out a good part of the race field.