X/XO stands for Xanthine/Xanthine Oxidase
X/F stands for Cross-Fade
X2O stands for Hexadecimal to Octal (conversion)
X/LBG stands for Xanthan/Locust Bean Gum
X/BAA stands for Accelerated Business Area Architecture
X-WAV stands for Unix Sound Format
X/OPEN stands for X/Open Company Ltd
X-XO stands for Xanthine Plus Xanthine Oxidase
X-SCID stands for X-Linked Severe Combined Immunodeficiency
X.25 stands for CCITT Packet Switching Protocol