Related Clues:

• Not the sharpest pencil in the box
• Not very sharp
• A few bricks shy of a load
• Highly concentrated
• Tough to get through to
• Hard to get through to
• Like a thicket
• Like heavy fog
• Closely crowded together
• Knuckleheaded
• Rather dense
• Really crammed in
• Greater than 90 degrees, as an angle
• Slow to catch on
• Crowded together