WordWeb Online

1. So great in size, force or extent as to elicit awe
   "a prodigious storm";
   - colossal, stupendous
    
2. Of momentous or ominous significance
   "a prodigious vision";
   - portentous
    
3. Far beyond what is usual in magnitude or degree
   "the young Mozart's prodigious talents";
   - exceeding, exceptional, olympian, surpassing

See also: big, extraordinary, important, large, significant

Encyclopedia: Prodigious