The Collaborative International Dictionary of English v.0.48:

Quaver \Qua"ver\, v. t.
   To utter with quavers.
   [1913 Webster]

         We shall hear her quavering them . . . to some
         sprightly airs of the opera.             --Addison.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Quaver \Qua"ver\, n.
   1. A shake, or rapid and tremulous vibration, of the voice,
      or of an instrument of music.
      [1913 Webster]

   2. (Mus.) An eighth note. See Eighth.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

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.
      [1913 Webster]

   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
      [1913 Webster]

WordNet (r) 3.0 (2006):

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