quack       
 verb [ I ] uk/kwæk/ us/kwæk/
 (鸭子)呱呱叫,嘎嘎叫
to make the usual sound of a duck
  The ducks started quacking loudly when we threw them some bread. 我们向那些鸭子扔面包时,它们呱呱地大叫起来。 
 quack  
noun [ C ] uk/kwæk/ us/kwæk/
  (PERSON)        
  disapproving冒牌医生,江湖医生,庸医 
a person who dishonestly pretends to have medical skills or knowledge
  UK informal often disapproving医生 
a doctor
  Have you seen a quack about that cough? 你去医生那儿看咳嗽了吗? 
   (SOUND)     
 [ C ](鸭子)呱呱叫,嘎嘎叫 
the sound that a duck makes