The Collaborative International Dictionary of English v.0.48:

Distinguish \Dis*tin"guish\, v. t. [imp. & p. p.
   Distinguished; p. pr. & vb. n. Distinguishing.] [F.
   distinguer, L. distinguere, distinctum; di- = dis- +
   stinguere to quench, extinguish; prob. orig., to prick, and
   so akin to G. stechen, E. stick, and perh. sting. Cf.
   Extinguish.]
   1. Not set apart from others by visible marks; to make
      distinctive or discernible by exhibiting differences; to
      mark off by some characteristic.
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            Not more distinguished by her purple vest,
            Than by the charming features of her face. --Dryden.
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            Milton has distinguished the sweetbrier and the
            eglantine.                            --Nares.
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   2. To separate by definition of terms or logical division of
      a subject with regard to difference; as, to distinguish
      sounds into high and low.
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            Moses distinguished the causes of the flood into
            those that belong to the heavens, and those that
            belong to the earth.                  --T. Burnet.
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   3. To recognize or discern by marks, signs, or characteristic
      quality or qualities; to know and discriminate (anything)
      from other things with which it might be confounded; as,
      to distinguish the sound of a drum.
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            We are enabled to distinguish good from evil, as
            well as truth from falsehood.         --Watts.
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            Nor more can you distinguish of a man,
            Than of his outward show.             --Shak.
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   4. To constitute a difference; to make to differ.
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            Who distinguisheth thee?              --1 Cor. iv.
                                                  7. (Douay
                                                  version).
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   5. To separate from others by a mark of honor; to make
      eminent or known; to confer distinction upon; -- with by
      or for."To distinguish themselves by means never tried
      before." --Johnson.

   Syn: To mark; discriminate; differentiate; characterize;
        discern; perceive; signalize; honor; glorify.
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The Collaborative International Dictionary of English v.0.48:

Distinguishing \Dis*tin"guish*ing\, a.
   Constituting difference, or distinction from everything else;
   distinctive; peculiar; characteristic.
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         The distinguishing doctrines of our holy religion.
                                                  --Locke.
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   Distinguishing pennant (Naut.), a special pennant by which
      any particular vessel in a fleet is recognized and
      signaled. --Simmonds.
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Moby Thesaurus II by Grady Ward, 1.0:

46 Moby Thesaurus words for "distinguishing":
   accurate, appreciative, characteristic, characterizing,
   contrastive, critical, delicate, diacritical, diagnostic,
   differencing, differential, differentiative, discriminate,
   discriminating, discriminative, distinctive, exact, exemplary,
   fastidious, fine, idiosyncratic, individualizing, individuating,
   natural, naturalistic, nice, normal, peculiar, personalizing,
   precise, quintessential, realistic, refined, regular, sample,
   selective, sensitive, separative, subtle, tactful, true to form,
   true to type, typal, typic, typical, usual