What is the meaning of retard?

noun

• A person of subnormal intelligence.
  • synonyms: idiot, imbecile, cretin, moron, changeling, half-wit

verb

• Cause to move more slowly or operate at a slower rate.
  • usage: "This drug will retard your heart rate"
• Be delayed.
• Slow the growth or development of.
  • usage: "The brain damage will retard the child's language development"
  • synonyms: check, delay
• Lose velocity; move more slowly.
  • usage: "The car decelerated"
  • synonyms: decelerate, slow, slow down, slow up