WX is an abbreviation for 'WeChat', a messaging app most commonly used by people from China.
The Chinese name for WeChat is 微信 (Wei Xin), which explains the reason for the 'X' in 'WX'.
wx is a scene word for if you see a hardcore kid who is possibly gay. A kid who is wx is a homosexual, and he is into hardcore music. You can see wx kids making out with eachother after concerts.