WordWeb Online

1. Far beyond what is usual in magnitude or degree
   "an exceptional memory"
   - exceeding, olympian, prodigious, surpassing
    
2. Surpassing what is common or usual or expected
   "exceptional kindness"
   - especial, particular, special
    
3. Deviating widely from a norm of physical or mental ability; used especially of children below normal in intelligence
   "special educational provisions for exceptional children"

See also: abnormal, exception, exceptionally, extraordinary, uncommon

Encyclopedia: Exceptional