The Collaborative International Dictionary of English v.0.48:

Demean \De*mean"\, v. t. [imp. & p. p. Demeaned; p. pr. & vb.
   n. Demeaning.] [OF. demener to conduct, guide, manage, F.
   se d['e]mener to struggle; pref. d['e]- (L. de) + mener to
   lead, drive, carry on, conduct, fr. L. minare to drive
   animals by threatening cries, fr. minari to threaten. See
   Menace.]
   1. To manage; to conduct; to treat.
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            [Our] clergy have with violence demeaned the matter.
                                                  --Milton.
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   2. To conduct; to behave; to comport; -- followed by the
      reflexive pronoun.
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            They have demeaned themselves
            Like men born to renown by life or death. --Shak.
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            They answered . . . that they should demean
            themselves according to their instructions.
                                                  --Clarendon.
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   3. To debase; to lower; to degrade; -- followed by the
      reflexive pronoun.
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            Her son would demean himself by a marriage with an
            artist's daughter.                    --Thackeray.
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   Note: This sense is probably due to a false etymology which
         regarded the word as connected with the adjective mean.
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The Collaborative International Dictionary of English v.0.48:

Demean \De*mean"\, n. [OF. demene. See Demean, v. t.]
   1. Management; treatment. [Obs.]
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            Vile demean and usage bad.            --Spenser.
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   2. Behavior; conduct; bearing; demeanor. [Obs.]
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            With grave demean and solemn vanity.  --West.
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The Collaborative International Dictionary of English v.0.48:

Demean \De*mean"\, n. [See Demesne.]
   1. Demesne. [Obs.]
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   2. pl. Resources; means. [Obs.]
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            You know
            How narrow our demeans are.           --Massinger.
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WordNet (r) 3.0 (2006):

demean
    v 1: reduce in worth or character, usually verbally; "She tends
         to put down younger women colleagues"; "His critics took
         him down after the lecture" [syn: take down, degrade,
         disgrace, demean, put down]

Moby Thesaurus II by Grady Ward, 1.0:

36 Moby Thesaurus words for "demean":
   abase, abash, acquit, act, bear, belittle, bring down, bring low,
   carry, cast down, comport, conduct, contemn, crush, debase, decry,
   degrade, deport, derogate, despise, detract, diminish, disparage,
   dump, dump on, go on, humiliate, lower, put down, quit, reduce,
   scorn, set down, sink, take down, trip up