" voicelessly "

1: as in silently, soundlessly;

•  Synonyms : 

•  inaudibly,

•  silently,

•  soundlessly,

•  faintly,

•  feebly,

•  low,

•  noiselessly,

•  quietly,

•  softly

•  Antonyms : 

•  aloud,

•  audibly,

•  out,

•  out loud,

•  verbally,

•  vocally,

•  clearly,

•  discernibly,

•  distinctly,

•  distinguishably,

•  perceptibly,

•  plainly

1: unable to speak;

  * e.g., " ... believes that animals deserve basic rights even though they are voiceless "

•  Synonyms : 

•  inarticulate,

•  mute,

•  speechless

•  Antonyms : 

• (N/A)