Related Clues:

• Imperturbable
• Poker-faced
• Hard to get to
• Solemn ceremony
• Unflinching
• Glass-half-empty type
• Bite-the-bullet type
• Distrustful sort
• Far from demonstrative
• Indifferent individual
• Not very excitable
• Forbearing
• Doubter
• Suspicious sourpuss
• Negative sort