Source : Webster's Revised Unabridged Dictionary (1913)

Ataraxia \At`a*rax"i*a\, Ataraxy \At"a*rax`y\, n. [NL. ataraxia,
   Gr. 'ataraxi`a; 'a priv. + tarakto`s disturbed, tara`ssein to
   disturb.]
   Perfect peace of mind, or calmness.