The Collaborative International Dictionary of English v.0.48:

Whispering \Whis"per*ing\,
   a. & n. from Whisper. v. t.
   [1913 Webster]

   Whispering gallery, or Whispering dome, one of such a
      form that sounds produced in certain parts of it are
      concentrated by reflection from the walls to another part,
      so that whispers or feeble sounds are audible at a much
      greater distance than under ordinary circumstances. The
      dome of the U. S. capitol building is one example.
      [1913 Webster +PJC]

The Collaborative International Dictionary of English v.0.48:

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[imac]skra, Sw. hviska, Dan.
   hviske; of imitative origin. Cf. Whistle.]
   [1913 Webster]
   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.
      [1913 Webster]

   2. To make a low, sibilant sound or noise.
      [1913 Webster]

            The hollow, whispering breeze.        --Thomson.
      [1913 Webster]

   3. To speak with suspicion, or timorous caution; to converse
      in whispers, as in secret plotting.
      [1913 Webster]

            All that hate me whisper together against me. --Ps.
                                                  xli. 7.
      [1913 Webster]

WordNet (r) 3.0 (2006):

whispering
    adj 1: making a low continuous indistinct sound; "like murmuring
           waves"; "susurrant voices" [syn: murmuring,
           susurrant, whispering]
    n 1: a light noise, like the noise of silk clothing or leaves
         blowing in the wind [syn: rustle, rustling, whisper,
         whispering]
    2: speaking softly without vibration of the vocal cords [syn:
       whisper, whispering, susurration, voicelessness]