Literary, a state of serene calmness; (also ataraxia).
A person is in a state of ataraxia when he or she is unable to have the slightest notion of worry or stress about a situation. It is more a spiritual or philosophical state than it is a psychological one; the term was first coined by the Greek philosophers Pyrrho and Epicurus. They believed that ataraxia led to a happier life, a life free of concern and ordinary setbacks. The Stoics also believed that ataraxia was something to be desired, but the term apatheia was used as well.
The word ataraxia (Anglicized ataraxy) comes from the Greek tarassein, meaning ‘to disturb’, with a- being the usual negative prefix.