Meaning of idiot savant

id•i•ot sa•vant

Pronunciation: (id'ē-ut sa-vänt', su-vant', sav'unt Fr. ē-dyō sa-vän'), [key]
— pl. id•i•ot sa•vants, id•i•ots sa•vants
  1. a mentally defective person with an exceptional skill or talent in a special field, as a highly developed ability to play music or to solve complex mathematical problems mentally at great speed.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.