One with so much shit between his/her ears they can't form rational thoughts or predictable behavior.
"Those guys from FTR (ie. Teen Acne, Vortex, Concept etc.) are a bunch of whining slugheads."
When a person's hair looks like a slug/ is the same shape as a slug.
Joe Beton's hair reminds Dougy Wurtfeld of a slug.
Joe Beton has a slughead.