| Acronyms | Meaning / Significance |
Source |
| X-Series | CCITT data communication network | |
| X-TELL | cross tell | |
| XI | exercise indicator | |
| XID | exchange identification | |
| XMIT | transmit | |
| XMITR | transmitter | |
| XML | eXtensible Markup Language | World Wide Web Consortium (W3C) |
| XML | exercise manning list | |
| XMSN | transmission | |
| XMT | exempt | |
| XOR | logical operator | |
| XSERV | aircraft x-servicing ample gain programme subsystem | |
| XTAL | crystal |