retard       
 verb [ T ]  formal uk/rɪˈtɑːd/ us/rɪˈtɑːrd/
 阻碍;减缓
to make something slower
  A rise in interest rates would severely retard economic growth. 利率提高会严重阻碍经济发展。 
 retard       
noun [ C ]  offensive uk/ˈriː.tɑːd/ us/ˈriː.tɑːrd/
 智力迟钝者;弱智;笨蛋
a stupid or mentally slow person
  I'm not playing with him, he's a total retard. 我才不跟他玩呢,他整个一大笨蛋。