retard in WordNet English dictionary

1. a person of subnormal intelligence
   idiot  imbecile  cretin  moron  changeling  half-wit  retard 
   

1. slow the growth or development of
   "The brain damage will retard the child's language development"
   check  retard  delay 
   
2. lose velocity; move more slowly
   "The car decelerated"
   decelerate  slow  slow down  slow up  retard 
   
3. cause to move more slowly or operate at a slower rate
   "This drug will retard your heart rate"
   retard 
   
4. be delayed
   retard