Related Clues:

• Unemotional
• Unvarying
• Unyielding
• Uncompromising
• Strict
• In a bind
• Kind of airship
• Baffled
• Zeno, notably
• One who grins and bears it
• Like Zeno
• Strait-laced
• Stiff-upper-lip type
• Zeno was one
• Long-suffering