Source : Free On-Line Dictionary of Computing

non-polynomial
     
         The set or property of problems for which no
        {polynomial-time algorithm} is known.
     
        This includes problems for which the only known {algorithm}s
        require a number of steps which increases exponentially with
        the size of the problem, and those for which no {algorithm} at
        all is known.  Within these two there are problems which are
        "{provably difficult}" and "{provably unsolvable}".
     
        (1995-04-10)