What is the meaning of retarded?

noun

• People collectively who are mentally retarded.
  • usage: "he started a school for the retarded"
  • synonyms: mentally retarded, developmentally challenged

verb

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

adjective

• Relatively slow in mental or emotional or physical development.
  • usage: "providing a secure and sometimes happy life for the retarded"