Source : WordNet®

natural language
     n : a human written or spoken language used by a community;
         opposed to e.g. a computer language [syn: {tongue}] [ant:
          {artificial language}]

Source : Free On-Line Dictionary of Computing

natural language
     
         A language spoken or written by humans, as
        opposed to a language use to program or communicate with
        computers.  Natural language understanding is one of the
        hardest problems of {artificial intelligence} due to the
        complexity, irregularity and diversity of human language and
        the philosophical problems of meaning.
     
        See also {Pleuk grammar development system}, {proof}.
     
        {An on-line demonstration (http://sakharov.ai.mit.edu/Start)}.
     
        {New York U
        (http://www.nyu.edu/pages/linguistics/ling.html)}.
     
        (1995-04-24)