X/OPEN SAG stands for X/Open SQL Access Group
X-SBMA stands for X-Linked Spinal and Bulbar Muscular Atrophy
X-SAR stands for X-Band Synthetic Aperture Radar
X.509 stands for Standard for Public-Key Infrastructure
X/Q stands for Relative Concentration
X.400 stands for CCITT Message Handling Protocol
X/W stands for X-Wing (Star Wars)
X-SAMPA stands for Extended Sampa
X.500 stands for CCITT Directory Services Protocol
X/WIND stands for Crosswind