nasal demons

nasal demons
 n.

   Recognized shorthand on the Usenet group comp.std.c for any unexpected
   behavior of a C compiler on encountering an undefined construct.
   During a discussion on that group in early 1992, a regular remarked
   "When the compiler encounters [a given undefined construct] it is
   legal for it to make demons fly out of your nose" (the implication is
   that the compiler may choose any arbitrarily bizarre way to interpret
   the code without violating the ANSI C standard). Someone else followed
   up with a reference to "nasal demons", which quickly became
   established. The original post is web-accessible at
   http://groups.google.com/groups?hl=en&selm=10195%40ksr.com.
    

nasal demons

   Recognised shorthand on the {Usenet} group comp.std.c for any
   unexpected behaviour of a {C} compiler on encountering an
   undefined construct.  During a discussion on that group in
   early 1992, a regular remarked "When the compiler encounters
   [a given undefined construct] it is legal for it to make
   demons fly out of your nose" (the implication is that the
   compiler may choose any arbitrarily bizarre way to interpret
   the code without violating the {ANSI C} {standard}).  Someone
   else followed up with a reference to "nasal demons", which
   quickly became established.

   [{Jargon File}]