资料来源 : pyDict

缺乏声调的,单调的,沈闷的

资料来源 : Webster's Revised Unabridged Dictionary (1913)

Toneless \Tone"less\, a.
   Having no tone; unmusical.

资料来源 : WordNet®

toneless
     adj : lacking in tone or expression; "his toneless mechanical
           voice" [ant: {toned}]