- XD is an emoticon used on the internet to express extreme happiness and/or laughter, in the league of 8D, -), ROFL and LMAO. As with almost all other smilies, one may tilt one's head to the left to see the face the letters create. In the case of "XD", if you tilt your head 90 degrees counterclockwise, you will see that the "X" mimics one's eyes squeezed shut with laughter, and the "D" represents one's mouth smiling widely. This is also the case for many other emoticons.
- XD_bit is a security-related computer technology for Intel processors which does not permit the execution of so-marked sections of memory in order to avoid the execution of possibly malicious instructions contained in data sections of program memory.
