The Collaborative International Dictionary of English v.0.48:

Singular \Sin"gu*lar\ (s[i^][ng]"g[-u]*l[~e]r), a. [OE.
   singuler, F. singulier, fr. L. singularius, singularis, fr.
   singulus single. See Single, a.]
   1. Separate or apart from others; single; distinct. [Obs.]
      --Bacon.
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            And God forbid that all a company
            Should rue a singular man's folly.    --Chaucer.
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   2. Engaged in by only one on a side; single. [Obs.]
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            To try the matter thus together in a singular
            combat.                               --Holinshed.
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   3. (Logic) Existing by itself; single; individual.
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            The idea which represents one . . . determinate
            thing, is called a singular idea, whether simple,
            complex, or compound.                 --I. Watts.
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   4. (Law) Each; individual; as, to convey several parcels of
      land, all and singular.
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   5. (Gram.) Denoting one person or thing; as, the singular
      number; -- opposed to dual and plural.
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   6. Standing by itself; out of the ordinary course; unusual;
      uncommon; strange; as, a singular phenomenon.
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            So singular a sadness
            Must have a cause as strange as the effect.
                                                  --Denham.
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   7. Distinguished as existing in a very high degree; rarely
      equaled; eminent; extraordinary; exceptional; as, a man of
      singular gravity or attainments.
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   8. Departing from general usage or expectations; odd;
      whimsical; -- often implying disapproval or censure.
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            His zeal
            None seconded, as out of season judged,
            Or singular and rash.                 --Milton.
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            To be singular in anything that is wise and worthy,
            is not a disparagement, but a praise. --Tillotson.
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   9. Being alone; belonging to, or being, that of which there
      is but one; unique.
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            These busts of the emperors and empresses are all
            very scarce, and some of them almost singular in
            their kind.                           --Addison.
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   Singular point in a curve (Math.), a point at which the
      curve possesses some peculiar properties not possessed by
      other points of the curve, as a cusp point, or a multiple
      point.

   Singular proposition (Logic), a proposition having as its
      subject a singular term, or a common term limited to an
      individual by means of a singular sign. --Whately.

   Singular succession (Civil Law), division among individual
      successors, as distinguished from universal succession, by
      which an estate descended in intestacy to the heirs in
      mass.

   Singular term (Logic), a term which represents or stands
      for a single individual.
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   Syn: Unexampled; unprecedented; eminent; extraordinary;
        remarkable; uncommon; rare; unusual; peculiar; strange;
        odd; eccentric; fantastic.
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The Collaborative International Dictionary of English v.0.48:

Singular \Sin"gu*lar\, n.
   1. An individual instance; a particular. [Obs.] --Dr. H.
      More.
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   2. (Gram) The singular number, or the number denoting one
      person or thing; a word in the singular number.
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WordNet (r) 3.0 (2006):

singular
    adj 1: unusual or striking; "a remarkable sight"; "such poise is
           singular in one so young" [syn: remarkable, singular]
    2: beyond or deviating from the usual or expected; "a curious
       hybrid accent"; "her speech has a funny twang"; "they have
       some funny ideas about war"; "had an odd name"; "the peculiar
       aromatic odor of cloves"; "something definitely queer about
       this town"; "what a rum fellow"; "singular behavior" [syn:
       curious, funny, odd, peculiar, queer, rum,
       rummy, singular]
    3: being a single and separate person or thing; "can the
       singular person be understood apart from his culture?";
       "every fact in the world might be singular...unlike any other
       fact and sole of its kind"-William James
    4: composed of one member, set, or kind [ant: plural]
    5: grammatical number category referring to a single item or
       unit [ant: plural]
    6: the single one of its kind; "a singular example"; "the unique
       existing example of Donne's handwriting"; "a unique copy of
       an ancient manuscript"; "certain types of problems have
       unique solutions" [syn: singular, unique]
    n 1: the form of a word that is used to denote a singleton [syn:
         singular, singular form] [ant: plural, plural form]