Related Clues:

• Highly concentrated
• Tough to get through to
• Hard to get through to
• Like a thicket
• Like heavy fog
• Closely crowded together
• Knuckleheaded
• Really crammed in
• *Jammed
• Slow to catch on
• Crowded together
• Thick, as fog
• Tough to get through
• Like a dumbbell
• Heavy, like some baked goods