Related Clues:

• Betraying no emotion
• Jaded sort
• Giving nothing away, in a way
• Uncomplaining sort
• Follower of the philosopher Epictetus
• Having a stiff upper lip
• Not overly emotional
• Not moved much
• Not reacting to pain, say
• Hard to stir
• Epictetus, for one
• Sarcastic sort
• Hard one to convince
• Marcus Aurelius was one
• One with a negative outlook on life