Used in
reference to an object or
thought moving at an
intense speed.
In some cases, the thought or thoughts tend to move
about in a chaotic manner,
not allowing for any type of conclusion to be drawn from them.
Hence they are racing around in circles almost, with no finish line in sight.
In this context, the process of thoughts racing can,
in some cases, drive one mad,
and leave them a hopeless victim to insomnia.