quaver in WordNet English dictionary

1. a musical note having the time value of an eighth of a whole note
   eighth note  quaver 
   
2. a tremulous sound
   quaver 
   

1. sing or play with trills, alternating with the half note above or below
   warble  trill  quaver 
   
2. give off unsteady sounds, alternating in amplitude or frequency
   quaver  waver