WordWeb Online

1. Incapable of being explained or accounted for
   "incomprehensible errors";
   - inexplicable
    
2. Difficult to understand
   "the most incomprehensible thing about the universe is that it is comprehensible";
   - uncomprehensible

See also: cryptic, cryptical, dark, deep, enigmatic, enigmatical, impenetrable, indecipherable, inscrutable, insoluble, lost, missed, muddy, mysterious, mystifying, obscure, opaque, paradoxical, puzzling, self-contradictory, unaccountable, unclear, unexplainable, unexplained, unfathomable, unintelligible

Antonym: explicable

Encyclopedia: Incomprehensible