A hangover that is so bad you can't even remember your phone number, pin number, etc.

I drank so much last night, I can't even remember where I parked. I've got some serious Brain Cloud today.
by B2thaHizo July 15, 2008
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The morning after a day of heavy weed smoking, where you can't focus on anything and your IQ drops 60 points.
Paul: Dude you drove the wrong way what were you thinking??
Danny: Sorry man I think I have cloud brain, I can't focus on anything.
by masterblanket March 24, 2015
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