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1.
When your brain runs about some issue over and over again and won't stop, just like a hamster running in its exercise wheel. It keeps running, but doesn't get anywhere.
I'm having such hamster wheel brain about whether or not to take this job offer.
by dward May 30, 2004
 
2.
an instance of one's mind going over and over an issue or problem without finding a solution
I had a major case hamster-wheel brain today. I could not get organized and could not stop thinking about it.
by The Return of Light Joker January 08, 2008