Source : Webster's Revised Unabridged Dictionary (1913)

Equanimous \E*quan"i*mous\, a. [L. aequanimus, fr. aequus equal
   + animus mind.]
   Of an even, composed frame of mind; of a steady temper; not
   easily elated or depressed. --Bp. Gauden.

Source : WordNet®

equanimous
     adj : in full control of your faculties; "the witness remained
           collected throughout the cross-examination"; "perfectly
           poised and sure of himself"; "more self-contained and
           more dependable than many of the early frontiersmen";
           "strong and self-possessed in the face of trouble"
           [syn: {collected}, {poised}, {self-collected}, {self-contained},
            {self-possessed}]