Source : Webster's Revised Unabridged Dictionary (1913)

Quaver \Qua"ver\, v. i. [imp. & p. p. {Quavered}; p. pr. & vb.
   n. {Quavering}.] [OE. quaven to shake, to tremble; cf. LG.
   quabbeln to shake, to be soft, of fat substances, quabbe a
   fat lump of flesh, a dewlap, D. kwabbe, and E. quiver, v.]
   1. To tremble; to vibrate; to shake. --Sir I. Newton.

   2. Especially, to shake the voice; to utter or form sound
      with rapid or tremulous vibrations, as in singing; also,
      to trill on a musical instrument

Quaver \Qua"ver\, v. t.
   To utter with quavers.

         We shall hear her quavering them . . . to some
         sprightly airs of the opera.             --Addison.

Quaver \Qua"ver\, n.
   1. A shake, or rapid and tremulous vibration, of the voice,
      or of an instrument of music.

   2. (Mus.) An eighth note. See {Eighth}.

Source : WordNet®

quaver
     n 1: a tremulous sound
     2: a musical note having the time value of an eighth of a whole
        note [syn: {eighth note}]
     v 1: give off unsteady sounds, alternating in amplitude or
          frequency [syn: {waver}]
     2: sing or play with trills, alternating with the half note
        above or below [syn: {warble}, {trill}]