The Collaborative International Dictionary of English v.0.48:

Interpolate \In*ter"po*late\, v. t. [imp. & p. p.
   Interpolated; p. pr. & vb. n. Interpolating.] [L.
   interpolatus, p. p. of interpolare to form anew, to
   interpolate, fr. interpolus, interpolis, falsified, vamped
   up, polished up; inter between + polire to polish. See
   Polish, v. t.]
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   1. To renew; to carry on with intermission. [Obs.]
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            Motion . . . partly continued and unintermitted, . .
            . partly interpolated and interrupted. --Sir M.
                                                  Hale.
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   2. To alter or corrupt by the insertion of new or foreign
      matter; especially, to change, as a book or text, by the
      insertion of matter that is new, or foreign to the purpose
      of the author.
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            How strangely Ignatius is mangled and interpolated,
            you may see by the vast difference of all copies and
            editions.                             --Bp. Barlow.
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            The Athenians were put in possession of Salamis by
            another law, which was cited by Solon, or, as some
            think, interpolated by him for that purpose. --Pope.
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   3. (Math.) To fill up intermediate terms of, as of a series,
      according to the law of the series; to introduce, as a
      number or quantity, in a partial series, according to the
      law of that part of the series; to estimate a value at a
      point intermediate between points of knwon value. Compare
      extrapolate.
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