The more information the brain holds, the more ceases it have. Flat brain literally mean that brain does not have any cease and contains next to nothing.

Often used to insult someone in a very rude way.
Person A: d(^ _ ^)b

Person B: how can you write that backward "b"?

Person A: ...what a flat brain you are.
by iCarrot September 25, 2010
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Flat Brained (Flatius Branium) is a common condition where the victim goes into a nearly catatonic state and shows no signs of brain activity, unable to achieve basic cognitive thought and anything above basic involuntary muscle work. Victims tend to constantly say and do utter nonsense and continue to do such until their vital organs eventually shut down.
Someone take the sandpaper away from Johnny, he's going to go flat brained again.
by GoldJohnnyBoi March 20, 2020
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