Related Clues:

• Hard to figure out
• Not quickly solved
• Stubborn, as a problem
• Tangled up
• Knotty
• Copy type
• Word with labor or candy
• Nearly unsolvable
• Word with boil or line
• "A ___ Day's Night"
• Verifiable, as facts
• Gnarled
• Intricate
• Baffling
• Opposite of soft