Source : Webster's Revised Unabridged Dictionary (1913)

Equanimity \E`qua*nim"i*ty\, n. [L. aequanimitas, fr.
   aequanimus: cf. F. ['e]quanimit['e]. See {Equanimous}.]
   Evenness of mind; that calm temper or firmness of mind which
   is not easily elated or depressed; patience; calmness;
   composure; as, to bear misfortunes with equanimity.

Source : WordNet®

equanimity
     n : steadiness of mind under stress; "he accepted their problems
         with composure and she with equanimity" [syn: {composure},
          {calm}, {calmness}] [ant: {discomposure}]