drone  
 noun uk/drəʊn/ us/droʊn/
  (NOISE)      
  [ S ]轰鸣声;嗡嗡声 
a low continuous noise that does not change its note
  the drone of an engine 发动机的轰鸣声 
 Outside the tent I could hear the constant drone of insects. 我能听到帐篷外面昆虫发出的持续不断的嗡嗡声。 
 The drone of his voice made me feel sleepy. 他单调低沉的语调让我昏昏欲睡。 
   (AIRCRAFT)      
  [ C ]无人驾驶飞机 
an aircraft that does not have a pilot but is controlled by someone on the ground, used especially for dropping bombs or for surveillance (= careful watching of a place)
  The U. S. Border Patrol's unmanned drone helped agents track down their smuggling suspect.
   (BEE)     
 [ C ]雄蜂 
a male bee
 drone       
verb [ I ] uk/drəʊn/ us/droʊn/
 发出轰鸣声;发出嗡嗡声
to make a low continuous noise that does not change its note
  An airplane droned in the background. 背景中响起了飞机的轰鸣声。 
 Phrasal verb   
drone on 喋喋不休,无休止地谈论
to talk for a long time in a boring way
  He was droning on (and on) about his operation. 他在喋喋不休地讲他的手术。