Source : Webster's Revised Unabridged Dictionary (1913)

Warble \War"ble\, v. t. [imp. & p. p. {Warbled}; p. pr. & vb. n.
   {Warbling}.] [OE. werbelen, OF. werbler; of Teutonic origin;
   cf. G. wirbeln to turn, to warble, D. wervelen, akin to E.
   whirl. See {Whirl}.]
   1. To sing in a trilling, quavering, or vibratory manner; to
      modulate with turns or variations; to trill; as, certain
      birds are remarkable for warbling their songs.

   2. To utter musically; to modulate; to carol.

            If she be right invoked in warbled song. --Milton.

            Warbling sweet the nuptial lay.       --Trumbull.

   3. To cause to quaver or vibrate. ``And touch the warbled
      string.'' --Milton.