| Abbreviation | Definition |
|---|---|
| XD1 | Cray high performance computing system |
| XDN | Xtras.Net Developer Network |
| XF | XML Framework |
| XIF | eXternal Interface File |
| XIG | XML Interest Group |
| XII | eXecution and Incomplete Information |
| XK-6 | Xtreme Keyboard 6 |
| XMAS | XML Matching And Structuring |
| XMFWG | eXtensible Music Format Working Group |
| XMP | Xml Message Protocol |
| XOR | logical Exclusive OR (programming, IC design) |
| XP | Xtreme Performance |
| XS | X Script |
| XTM | Xml Topic Maps |
| XTML | Xtensible Telephony Markup Language |
| XTP | eXtreme Transaction Processing |
| XUG | Xbox Users Group |
| XVGA | Extended Video Graphics Array |
| Y2K | Year 2000 |
| Y2M | You're too Much |