The tendency for marketing departments and technologists to prefix product names with the letter 'X' in order to indicate that they are futuristic, ''cool'' and generally better than everything else. There is also a tendency for people to believe them. If the full name of the product begins with 'Ex' this gives a second weak justification for the moniker (e.g., 'Extensible', 'Experience', 'Extreme').

'''Xamples:'''
* X-Files - A fictional TV program.
* X-Box - A Microsoft games console that's really just a cut down out-of-date PC.
* X-Windows - A windowing system for UNIX.
** ''Actually, this is was a modification to an earlier W windowing system, sorta like CeeLanguage was an improved B language.''
* XML - A data format based on a document markup language based on another document markup language.
* XR3i - An 80s Ford Escort that didn't go as fast as a Golf GTi and didn't handle as well either.
* X-Men - A fictional comic book series (now made into films).
* X-Prize - A prize for the first privately-funded space-shot.
* XP - A version of Windows, forced on Microsoft because of YtwokErrors with their previous naming strategy.  ''But they had little problem calling a version Windows 2000''
* ExtremeProgramming?  OK, there's an E in front of that X, but you get the picture.
* XMP - An XML-based MetaData standard.
* Mac OS X - Roman era computing! Rumor: next version to be expressed in unary. ;)

''and more''.