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]

Moby Thesaurus II by Grady Ward, 1.0:

154 Moby Thesaurus words for "singular":
   a certain, abnormal, absolute, absurd, alone, an, anomalous, any,
   any one, appropriate, atomic, atypical, azygous, bizarre, celibate,
   certain, characteristic, concrete, conspicuous, crank, crankish,
   cranky, crotchety, curious, defined, definite, detailed,
   determinate, deviant, deviative, different, discrete, distinct,
   distinctive, distinguished, divergent, dotty, dual, eccentric,
   either, eminent, erratic, esoteric, especial, exceptional,
   exclusive, express, extraordinary, fey, first and last, fixed,
   flaky, freaked out, freakish, freaky, funny, idiocratic,
   idiosyncratic, impair, important, in character, individual,
   indivisible, inner, integral, intimate, intrinsic, irreducible,
   irregular, isolated, kinky, kooky, lone, maggoty, marked, minute,
   monadic, monistic, notable, noteworthy, number, nutty, odd,
   oddball, off, off the wall, offbeat, one, one and only, only,
   only-begotten, out, outlandish, outre, outstanding, particular,
   passing strange, peculiar, personal, plural, precise, private,
   prominent, proper, quaint, queer, quintessential, quirky, rare,
   remarkable, respective, screwball, screwy, separate, several,
   signal, significant, simple, single, sole, solid, solipsistic,
   solitary, solo, special, specific, strange, superior, trial,
   true to form, twisted, unanalyzable, uncommon, unconventional,
   undivided, unearthly, unexampled, uniform, unimaginable, unique,
   unitary, unnatural, unordinary, unpaired, unrepeatable, unrepeated,
   unthinkable, unusual, unwonted, wacky, weird, whimsical, whole,
   wondrous strange



Bouvier's Law Dictionary, Revised 6th Ed (1856):

SINGULAR, construction. In grammar the singular is used to express only one,
not plural. Johnson.
     2. In law, the singular frequently includes the plural. A bequest to
"my nearest relation," for example, will be considered as a bequest to all
the relations in the same degree, who are nearest to the testator. 1 Ves.
sen. 337; 1 Bro. C. C. 293. A bequest made to "my heir," by a person who had
three heirs, will be construed in the plural. 4 Russ. C. C. 384.
     3. The same rule obtains in the civil law: In usu juris frequenter uti
nos singulari appellationie, am plura significari vellemus. Dig. 50, l6,
158.