numskull or numbskull /numˈskul/ (informal)

A blockhead

• screw bolt
• screw bolts
• screw cap
• screw-capped
• screw caps
• screw-down
• screwdriver
• screwdrivers
• screwed
• screwer
• screwers
• screw eye
• screw eyes
• screwier
• screwiest
• screwiness
• screwing
• screwing dice
• screwing die
• screwing machine
• screwing machines
• screwings
• screw it
• screw jack
• screw jacks