X

X /X/ n.  1. Used in various speech and writing contexts
   (also in lowercase) in roughly its algebraic sense of `unknown
   within a set defined by context' (compare {N}).  Thus, the
   abbreviation 680x0 stands for 68000, 68010, 68020, 68030, or 68040,
   and 80x86 stands for 80186, 80286 80386 or 80486 (note that a UNIX
   hacker might write these as 680[0-4]0 and 80[1-4]86 or 680?0 and
   80?86 respectively; see {glob}).  2. [after the name of an
   earlier window system called `W'] An over-sized, over-featured,
   over-engineered and incredibly over-complicated window system
   developed at MIT and widely used on UNIX systems.