In Call of Duty, Modern Warfare 2, Captain Price asks Yuri to shoot two men using his sniper rifle. He first draws Yuri's attention to their location by saying, "Two x-rays, 11 o'clock." And then commands to kill those, "Take them out." I don't understand x-rays here! I googled it so many times but got nothing. It wasn't dark and they weren't wearing night vision goggles, so that possibility is also out. Anyone is familiar with such term and it's usage here?
In context it's clear that by "X-ray" they mean "possible enemies" or "possible targets". It's military slang.
The question is, why "X-ray"? This is most likely related to the military phonetic alphabet, in which X-RAY stands for the letter "X". "X" is commonly used in English to refer to "unidentified" or "secret" objects (and so sounds vaguely "cool"), but in this case it's possible that 'X" stands for "eXtremist" -- meaning "rogue" soldiers who are not part of any official state-sponsored military.
In a similar way, certain militaries (or at least, games supposedly based on the military) use "Tango" to refer to certain enemies. TANGO is the military phonetic term for the letter "T", which may refer to "terrorist" or "target".
Note that in other games "X-ray" might refer to "eXtraterrestrials", meaning aliens.
X-ray is the phonetic pronunciation of the letter X in military speak. Basically just preventing miscommunication over noisy channels. This may just be Call of Duty being Call of Duty and trying to sprinkle as much military speak as possible into the game. Check out this: wikipedia article