Top Definition
A condition where the sufferer demonstrates erratic, odd or atypical behaviour, attributable to the swelling of the brain.

Known cures: compensatory pressure applied to the head by a compressive band.
"Did you see Tom Cruise jumpin up and down on Oprah's couch? He must have mentalpetoblyism."

"Sally must be trying to cure her mentalpetoblyism. OTherwise that's one stupid looking head band"
by Tipper Thorburn September 13, 2006

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