Source : Webster's Revised Unabridged Dictionary (1913)

Whisper \Whis"per\, v. t.
   1. To utter in a low and nonvocal tone; to say under the
      breath; hence, to mention privately and confidentially, or
      in a whisper.

            They might buzz and whisper it one to another.
                                                  --Bentley.

   2. To address in a whisper, or low voice. [Archaic]

            And whisper one another in the ear.   --Shak.

            Where gentlest breezes whisper souls distressed.
                                                  --Keble.

   3. To prompt secretly or cautiously; to inform privately.
      [Obs.] ``He came to whisper Wolsey.'' --Shak.

Whisper \Whis"per\, v. i. [imp. & p. p. {Whispered}; p. pr. &
   vb. n. {Whispering}.] [AS. hwisprian; akin to G. wispern,
   wispeln, OHG. hwispal?n, Icel. hv[=i]skra, Sw. hviska, Dan.
   hviske; of imitative origin. Cf. {Whistle}.]
   1. To speak softly, or under the breath, so as to be heard
      only by one near at hand; to utter words without sonant
      breath; to talk without that vibration in the larynx which
      gives sonorous, or vocal, sound. See {Whisper}, n.

   2. To make a low, sibilant sound or noise.

            The hollow, whispering breeze.        --Thomson.

   3. To speak with suspicion, or timorous caution; to converse
      in whispers, as in secret plotting.

            All that hate me whisper together against me. --Ps.
                                                  xli. 7.

Whisper \Whis"per\, n.
   1. A low, soft, sibilant voice or utterance, which can be
      heard only by those near at hand; voice or utterance that
      employs only breath sound without tone, friction against
      the edges of the vocal cords and arytenoid cartilages
      taking the place of the vibration of the cords that
      produces tone; sometimes, in a limited sense, the sound
      produced by such friction as distinguished from breath
      sound made by friction against parts of the mouth. See
      {Voice}, n., 2, and Guide to Pronunciation, [sect][sect]
      5, 153, 154.

            The inward voice or whisper can not give a tone.
                                                  --Bacon.

            Soft whispers through the assembly went. --Dryden.

   2. A cautious or timorous speech. --South.

   3. Something communicated in secret or by whispering; a
      suggestion or insinuation.

   4. A low, sibilant sound. ``The whispers of the leaves.''
      --Tennyson.

Source : WordNet®

whisper
     n 1: speaking softly without vibration of the vocal cords [syn: {whispering},
           {susurration}]
     2: the light noise like the noise of silk clothing or leaves
        blowing in the wind [syn: {rustle}, {rustling}, {whispering}]
     v : speak softly; in a low voice [ant: {shout}]