Definitions of "Head a gadda wata"

Has/Have a mental disability

Patois: It seem like him head a gadda wata
English: It seems like he has a mental disability

Mentally challenged

A person who has a learning disability. Literal translation; his head is gathering water.

Patois: Cuse mi sah,yuh pickney head a gadda wata.
English: Excuse me sir, your child has a learning disability.