The X.Org project provides an open source implementation of the X Window System. The development work is being done in conjunction with the freedesktop.org community.
http://www.x.org/

X is the twenty-fourth letter in the modern Latin alphabet. Its name in English is spelled ex or occasionally ecks (pronounced /?ks/), plural exes.
http://en.wikipedia.org/wiki/X

X is a noted punk rock band, formed in Los Angeles in 1977. While they achieved only limited mainstream success, they were widely considered one of the most accessible and tuneful ...
http://en.wikipedia.org/wiki/X_%28U.S._band%29

Leopard collects hundreds of features into one OS so innovative, it will completely transform your Mac. A dramatic new desktop. One-click data time travel. The power to see inside ...
http://www.apple.com/macosx/

Get detailed information on UNITED STATES STEEL (X) including quote performance, Real-Time ECN, technical chart analysis, key stats, insider transactions, and the latest company ...
http://finance.yahoo.com/q?s=x&d=t