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}]
Source: WordNet® 2.0