A cutoff, upper-air low occurs when a counterclockwise wind circulation becomes separated from the main stream of west-to-east winds in the jet stream.
When this happens, the storm has nothing to push it out, so it sits and spins for days at a time.
These types of storms often deliver plenty of clouds along with scattered showers. When situated along the coast, heavy rain, high winds and large waves are possible.
A Nor'Easter is often a cut-off low, which can deliver pounding surf and significant wind and snowfall.
Cut-off lows will continue to spin until the upper-level winds become prominent enough to "push" the storm away.
Often, the storm will spin-out and dissipate, or weaken, long before it's moved out.