Related Clues:

• Boneheaded
• Jam-packed
• Thick headed
• Heavily populated
• Like urban populations
• Crammed in
• Hard to see through
• Like a boor
• Far from 22-Down
• Overgrown
• Hard to see through, as fog
• One way to lay it on
• A little on the slow side
• Not sparse
• Not Mensa material