informant

informant
    n 1: a person who supplies information [syn: {informant},
         {source}]
    2: someone who sees an event and reports what happened [syn:
       {witness}, {witnesser}, {informant}]
    

Informant \In*form"ant\, n. [L. informans, -antis, p. pr. of
   informare. See {Inform}, v. t.]
   1. One who, or that which, informs, animates, or vivifies.
      [Obs.] --Glanvill.
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   2. One who imparts information or instruction.
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   3. One who offers an accusation; an informer. See {Informer}.
      [Obs. or R.]
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            It was the last evidence of the kind; the informant
            was hanged.                           --Burke.
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51 Moby Thesaurus words for "informant":
      adviser, announcer, annunciator, attestant, attestator, attester,
      authority, bystander, channel, cojuror, communicant, communicator,
      compurgator, deponent, earwitness, enlightener, examinant,
      examinate, examinee, expert witness, eyewitness, gossipmonger,
      grapevine, information center, information medium, informer,
      interviewee, monitor, mouthpiece, newsmonger, notifier, passerby,
      press, public relations officer, publisher, questionee, quizzee,
      radio, reporter, source, spectator, spokesman, subject, swearer,
      television, teller, testifier, tipster, tout, voucher, witness