Source : Webster's Revised Unabridged Dictionary (1913)

Testify \Tes"ti*fy\, v. i. [imp. & p. p. {Testified}; p. pr. &
   vb. n. {Testifying}.] [OF. testifier, L. testificari; testis
   a witness + -ficare (in comp.) to make. See {-fy}, and cf.
   {Attest}, {Contest}, {Detest}, {Protest}, {Testament}.]
   1. To make a solemn declaration, verbal or written, to
      establish some fact; to give testimony for the purpose of
      communicating to others a knowledge of something not known
      to them.

            Jesus . . . needed not that any should testify of
            man, for he knew what was in man.     --John ii. 25.

   2. (Law) To make a solemn declaration under oath or
      affirmation, for the purpose of establishing, or making
      proof of, some fact to a court; to give testimony in a
      cause depending before a tribunal.

            One witness shall not testify against any person to
            cause him to die.                     --Num. xxxv.
                                                  30.

   3. To declare a charge; to protest; to give information; to
      bear witness; -- with against.

            O Israel, . . . I will testify against thee. --Ps.
                                                  l. 7.

            I testified against them in the day wherein they
            sold victuals.                        --Neh. xiii.
                                                  15.

Testify \Tes"ti*fy\, adv.
   In a testy manner; fretfully; peevishly; with petulance.

Testify \Tes"ti*fy\, v. t.
   1. To bear witness to; to support the truth of by testimony;
      to affirm or declare solemny.

            We speak that we do know, and testify that we have
            seen; and ye receive not our witness. --John iii.
                                                  11.

   2. (Law) To affirm or declare under oath or affirmation
      before a tribunal, in order to prove some fact.

Source : WordNet®

testify
     v 1: give testimony in a court of law [syn: {attest}, {take the
          stand}, {bear witness}]
     2: provide evidence for; "The blood test showed that he was the
        father"; "Her behavior testified to her incompetence"
        [syn: {bear witness}, {prove}, {evidence}, {show}]
     [also: {testified}]