Source : Webster's Revised Unabridged Dictionary (1913)

Falsify \Fal"si*fy\, v. t. [imp. & p. p. {Falsified}; p. pr. &
   vb. n. {Falsifying}.] [L. falsus false + -ly: cf. F.
   falsifier. See {False}, a.]
   1. To make false; to represent falsely.

            The Irish bards use to forge and falsify everything
            as they list, to please or displease any man.
                                                  --Spenser.

   2. To counterfeit; to forge; as, to falsify coin.

   3. To prove to be false, or untrustworthy; to confute; to
      disprove; to nullify; to make to appear false.

            By how much better than my word I am, By so much
            shall I falsify men's hope.           --Shak.

            Jews and Pagans united all their endeavors, under
            Julian the apostate, to baffie and falsify the
            prediction.                           --Addison.

   4. To violate; to break by falsehood; as, to falsify one's
      faith or word. --Sir P. Sidney.

   5. To baffle or escape; as, to falsify a blow. --Butler.

   6. (Law) To avoid or defeat; to prove false, as a judgment.
      --Blackstone.

   7. (Equity) To show, in accounting, (an inem of charge
      inserted in an account) to be wrong. --Story. Daniell.

   8. To make false by multilation or addition; to tamper with;
      as, to falsify a record or document.

Falsify \Fal"si*fy\, v. i.
   To tell lies; to violate the truth.

         It is absolutely and universally unlawful to lie and
         falsify.

         South.

Source : WordNet®

falsify
     v 1: make false by mutilation or addition; as of a message or
          story [syn: {distort}, {garble}, {warp}]
     2: fake or falsify; "Fudge the figures"; "cook the books";
        "falsify the data" [syn: {fudge}, {manipulate}, {fake}, {cook},
         {wangle}, {misrepresent}]
     3: prove false; "Falsify a claim"
     4: falsify knowingly; "She falsified the records" [ant: {correct}]
     5: insert words into texts, often falsifying it thereby [syn: {interpolate},
         {alter}]
     [also: {falsified}]