Poor memory or inattention displayed by someone not old or adled enough to be suffering full Alzheimer's disease. Half of the poor memory usually associated with Alzheimer's.
"It was a shame how Hal acted in that meeting today after not reading the prep materials. He clearly wasn't listening to the discussion. He sounded like he had halfheimer's."
Rosies friends:OH LOOK rosie is your lover Berty halfhead
Berty halfhead: tries to impress rosie by opening their mouths and pulling his pants down and shitting in their mouths
Rosie: EWW WTF BERTY I LIKED U
Berty: Kisses her mouth with shit on it Rosie: runs while crying.
Everyone that was watching:knowing how short his dick is and laughing at him.