Source : Webster's Revised Unabridged Dictionary (1913)

Cretin \Cre"tin\ (kr[=e]"t[i^]n), n. [F. cr['e]tin; of uncertain
   origin.]
   One afflicted with cretinism.

Source : WordNet®

cretin
     n : a person of subnormal intelligence [syn: {idiot}, {imbecile},
          {moron}, {changeling}, {half-wit}, {retard}]