Related Clues:
- Seneca, for one
- Unemotional thinker
- Devoid of emotion
- Hard to rattle
- Showing little emotion
- Not easily flapped
- Betraying no emotion
- 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