The Oxford Thesaurus An A-Z Dictionary of Synonyms - quaverv.

1) tremble, quiver, shake, shiver, vibrate, waver, shudder, fluctuate, oscillate, flutter: His voice quavered with emotion as he described his rescue. --n. 2) trembling, tremble, quiver, quivering, tremor, shaking, vibration, wavering, break, fluctuation, oscillation: Only a slight quaver in her voice betrayed her feeling of panic.