Source : Free On-Line Dictionary of Computing

blivet
     
        /bliv'*t/ [allegedly from a World War II military term meaning
        "ten pounds of manure in a five-pound bag"] 1. An intractable
        problem.
     
        2. A crucial piece of hardware that can't be fixed or replaced
        if it breaks.
     
        3. A tool that has been hacked over by so many incompetent
        programmers that it has become an unmaintainable tissue of
        hacks.
     
        4. An out-of-control but unkillable development effort.
     
        5. An embarrassing bug that pops up during a customer demo.
     
        6. In the subjargon of computer security specialists, a
        denial-of-service attack performed by hogging limited
        resources that have no access controls (for example, shared
        spool space on a multi-user system).
     
        This term has other meanings in other technical cultures;
        among experimental physicists and hardware engineers of
        various kinds it seems to mean any random object of unknown
        purpose (similar to hackish use of {frob}).  It has also been
        used to describe an amusing trick-the-eye drawing resembling a
        three-pronged fork that appears to depict a three-dimensional
        object until one realises that the parts fit together in an
        impossible way.
     
        [{Jargon File}]