The Collaborative International Dictionary of English v.0.48:

Demeanor \De*mean"or\, n. [Written also demeanour.] [For
   demeanure, fr. demean. See Demean, v. t.]
   1. Management; treatment; conduct. [Obs.]
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            God commits the managing so great a trust . . .
            wholly to the demeanor of every grown man. --Milton.
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   2. Behavior; deportment; carriage; bearing; mien.
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            His demeanor was singularly pleasing. --Macaulay.
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            The men, as usual, liked her artless kindness and
            simple refined demeanor.              --Thackeray.
      [1913 Webster]

WordNet (r) 3.0 (2006):

demeanor
    n 1: (behavioral attributes) the way a person behaves toward
         other people [syn: demeanor, demeanour, behavior,
         behaviour, conduct, deportment]

Moby Thesaurus II by Grady Ward, 1.0:

74 Moby Thesaurus words for "demeanor":
   action, actions, activity, acts, address, affectation, air,
   bearing, behavior, behavior pattern, behavioral norm,
   behavioral science, brow, carriage, cast, cast of countenance,
   color, complexion, comportment, conduct, countenance,
   culture pattern, custom, deportment, doing, doings, face,
   facial appearance, favor, feature, features, folkway, garb,
   gestures, goings-on, guise, lineaments, lines, looks, maintien,
   manner, manners, method, methodology, methods, mien, modus vivendi,
   motions, movements, moves, observable behavior, pattern,
   physiognomy, poise, port, pose, posture, practice, praxis,
   presence, procedure, proceeding, set, social science, stance,
   style, tactics, tone, traits, turn, visage, way, way of life,
   ways