The Collaborative International Dictionary of English v.0.48:

Comportment \Com*port"ment\, n. [F. comportement.]
   Manner of acting; behavior; bearing.
   [1913 Webster]

         A graceful comportment of their bodies.  --Cowley.
   [1913 Webster]

         Her serious and devout comportment.      --Addison.
   [1913 Webster]

WordNet (r) 3.0 (2006):

comportment
    n 1: dignified manner or conduct [syn: bearing, comportment,
         presence, mien]

Moby Thesaurus II by Grady Ward, 1.0:

54 Moby Thesaurus words for "comportment":
   action, actions, activity, acts, address, affectation, air,
   bearing, behavior, behavior pattern, behavioral norm,
   behavioral science, carriage, conduct, culture pattern, custom,
   demeanor, deportment, doing, doings, folkway, gestures, goings-on,
   guise, maintien, manner, manners, method, methodology, methods,
   mien, modus vivendi, motions, movements, moves,
   observable behavior, pattern, poise, port, pose, posture, practice,
   praxis, presence, procedure, proceeding, set, social science,
   style, tactics, tone, way, way of life, ways