Source : Webster's Revised Unabridged Dictionary (1913)

Retard \Re*tard"\, v. i.
   To stay back. [Obs.] --Sir. T. Browne.

Retard \Re*tard"\, n.
   Retardation; delay.

Retard \Re*tard"\, v. t. [imp. & p. p. {Retarded}; p. pr. & vb.
   n. {Retarding}.] [L. retardare, retardatum; pref. re- re- +
   tardare to make slow, to delay, fr. tardus slow: cf. F.
   retarder. See {Tardy}.]
   1. To keep delaying; to continue to hinder; to prevent from
      progress; to render more slow in progress; to impede; to
      hinder; as, to retard the march of an army; to retard the
      motion of a ship; -- opposed to {accelerate}.

   2. To put off; to postpone; as, to retard the attacks of old
      age; to retard a rupture between nations.

   Syn: To impede; hinder; obstruct; detain; delay;
        procrastinate; postpone; defer.

Source : WordNet®

retard
     n : a person of subnormal intelligence [syn: {idiot}, {imbecile},
          {cretin}, {moron}, {changeling}, {half-wit}]
     v 1: slow the growth or development of; "The brain damage will
          retard the child's language development" [syn: {check},
          {delay}]
     2: cause to move more slowly or operate at a slower rate; "This
        drug will retard your heart rate"
     3: be delayed
     4: lose velocity; move more slowly; "The car decelerated" [syn:
         {decelerate}, {slow}, {slow down}, {slow up}] [ant: {accelerate}]