Savant

A savant is a learned person, well versed in literature or science, often with an exceptional skill in a specialized field of learning. The term is also commonly used as an abbreviation of autistic savant, formerly "idiot savant". The word is a loanword from the French language.

Source: http://en.wikipedia.org/wiki/Savant

Example: Rain man

An autistic savant (historically described as idiot savant) is a person with extraordinary mental abilities, often in numerical calculation, but sometimes in art or music. These skills are often, yet not exclusively, associated with mental retardation, and low I.Q.

Source: http://en.wikipedia.org/wiki/Autistic_savant

中譯: 白痴天才