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Deadly Disc if you mean the sort not housed in a power tool.
Also somewhat truth in television; the combination of extreme angular momentum and gyroscopic stabilization is a dangerous thing. Spinning things are like batteries that store energy as angular momentum
If a wheel-like object somehow comes free of its mount while running at hundreds or thousands of RPM, it can and will accelerate along the ground until all of the energy stored in it has been expended either by conversion into linear momentum or as work in the form of cutting through and/or embedding itself into something. The gyroscopic effect will keep it upright and moving straight for the same reason that if the wheels are spinning fast enough a motorcycle can right itself and drive for a while after a wipeout. (This is part of why I like oscillating saws.)
Exactly what the title says. If you still don't understand, it's basically singular buzzsaws that somehow keep moving (or even accelerate) on their own for unusually long distances.