A term used in counterstrike to denote a server command (regardless of whether it actually exists). The '0' means 'OFF' and '1' means 'ON', thus cl_cry 0 is a humorous, albeit geeky way to ask somebody to stop crying/moaning in-game.
Any word can substitute 'cry' depending upon the circumstances, such as cl_whine 0 etc.
player 1: Zomg ffs, he glocked me from 100 yards again!
player 2: cl_cry 0
player 3: Wahaha pwnt.