1. 
[syn: collected, equanimous, poised, self-collected, self-contained, self-possessed]
The Collaborative International Dictionary of English v.0.48:
Self-possessed \Self"-pos*sessed"\, a.
   Composed or tranquil in mind, manner, etc.; undisturbed.
   [1913 Webster]
WordNet (r) 3.0 (2006):
self-possessed
    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]
Moby Thesaurus II by Grady Ward, 1.0:
47 Moby Thesaurus words for "self-possessed":
   aloof, assured, balanced, calm, collected, composed, confident,
   controlled, cool, detached, dignified, easy, easygoing, equanimous,
   equilibrious, even-tempered, firm-minded, forward, imperturbable,
   importunate, independent, levelheaded, peaceful, placid, poised,
   pushy, recollected, refined, reserved, self-asserting,
   self-assertive, self-assured, self-confident, self-contained,
   self-controlled, self-expressive, self-restrained, serene,
   strong-minded, strong-willed, together, tranquil, undisturbed,
   unflappable, unperturbed, unruffled, well-balanced