The Collaborative International Dictionary of English v.0.48:

Fraction \Frac"tion\, n. [F. fraction, L. fractio a breaking,
   fr. frangere, fractum, to break. See Break.]
   1. The act of breaking, or state of being broken, especially
      by violence. [Obs.]
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            Neither can the natural body of Christ be subject to
            any fraction or breaking up.          --Foxe.
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   2. A portion; a fragment.
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            Some niggard fractions of an hour.    --Tennyson.
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   3. (Arith. or Alg.) One or more aliquot parts of a unit or
      whole number; an expression for a definite portion of a
      unit or magnitude.
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   Common fraction, or Vulgar fraction, a fraction in which
      the number of equal parts into which the integer is
      supposed to be divided is indicated by figures or letters,
      called the denominator, written below a line, over which
      is the numerator, indicating the number of these parts
      included in the fraction; as 1/2, one half, 2/5, two
      fifths.

   Complex fraction, a fraction having a fraction or mixed
      number in the numerator or denominator, or in both.
      --Davies & Peck.

   Compound fraction, a fraction of a fraction; two or more
      fractions connected by of.

   Continued fraction, Decimal fraction, Partial fraction,
      etc. See under Continued, Decimal, Partial, etc.

   Improper fraction, a fraction in which the numerator is
      greater than the denominator.

   Proper fraction, a fraction in which the numerator is less
      than the denominator.
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The Collaborative International Dictionary of English v.0.48:

Improper \Im*prop"er\, a. [F. impropre, L. improprius; pref. im-
   not + proprius proper. See Proper.]
   1. Not proper; not suitable; not fitted to the circumstances,
      design, or end; unfit; not becoming; incongruous;
      inappropriate; indecent; as, an improper medicine;
      improper thought, behavior, language, dress.
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            Follow'd his enemy king, and did him service,
            Improper for a slave.                 --Shak.
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            And to their proper operation still,
            Ascribe all Good; to their improper, Ill. --Pope.
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   2. Not peculiar or appropriate to individuals; general;
      common. [Obs.]
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            Not to be adorned with any art but such improper
            ones as nature is said to bestow, as singing and
            poetry.                               --J. Fletcher.
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   3. Not according to facts; inaccurate; erroneous.
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   Improper diphthong. See under Diphthong.

   Improper feud, an original feud, not earned by military
      service. --Mozley & W.

   Improper fraction. See under Fraction.
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WordNet (r) 3.0 (2006):

improper fraction
    n 1: a fraction whose numerator is larger than the denominator