Source : Webster's Revised Unabridged Dictionary (1913)

Demeanor \De*mean"or\, n. [Written also {demeanour}.] [For
   demeanure, fr. demean. See {Demean}, v. t.]
   1. Management; treatment; conduct. [Obs.]

            God commits the managing so great a trust . . .
            wholly to the demeanor of every grown man. --Milton.

   2. Behavior; deportment; carriage; bearing; mien.

            His demeanor was singularly pleasing. --Macaulay.

            The men, as usual, liked her artless kindness and
            simple refined demeanor.              --Thackeray.

Source : WordNet®

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