Related Clues:

• Hard to penetrate
• In a quandary
• Crammed
• In a jam
• Unable to move
• Needs another way?
• Concentrated
• None too swift
• Hardly suited for Mensa
• Mired
• Immovable
• Slow to understand
• Not the brightest bulb on the Christmas tree
• Sold-out show
• Thickly populated