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):

whispered
    adj 1: spoken in soft hushed tones without vibrations of the
           vocal cords; "a long whispered conversation"