It basically means
No Good; Cannot Understand

Is normally used for foreign languages used on a forum.
<David> Hey, what was that thread about last night?
<Joseph> Já nevím, som čítal, že téma...
<Tristan> ng;cu
<David> NG;CU
<Tristan> Lol, inb4
by TheFinalDegree April 5, 2009
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