blivet: /bliv'*t/ [allegedly from a World War II military term meaning "ten pounds of manure in a five-pound bag"] n

:blivet: /bliv'*t/ [allegedly from a World War II military term
meaning "ten pounds of manure in a five-pound bag"] n. 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 realizes
that the parts fit together in an impossible way.
-- The AI Hackers Dictionary