Related Clues:

• Axis enciphering machine
• Baffling question
• It's hard to understand
• Riddle relative
• Tough nut to crack
• It's not clear
• Tough one
• "Cheese" sayer
• Tough problem
• It's not easy
• Puzzling person
• Puzzling problem
• You figure it out
• Show-off
• Sieve