Related Clues:

• Obtuse
• Overpowering
• None too smart
• Like thick fog
• Tightly packed
• Fervid
• Not too bright
• Not too astute
• Slow on the uptake
• Not the brightest bulb on the tree
• Hardly qualified to be a rocket scientist
• Doltish
• Stupid
• ...
• Thick as a brick