equanimous

from WordNet (r) 3.0 (2006)

equanimous
    adj 1: 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}, {equanimous}, {poised}, {self-collected},
           {self-contained}, {self-possessed}]

from The Collaborative International Dictionary of English v.0.48

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.
   [1913 Webster]