kthx
The root "word" of several kthx* phrases. (such as kthxbye and kthxdie) Commonly used in IRC chats to express sarcastic lameness, implying that you're having to step down to talking "their" language when addressing a lamer.
Example:
HAY CAN U HELP ME INTSALL LUNIX FOR WONDOWS?
kthxrtfmplz
KTHXSTFU
* Op has banned *llama*@*
* llama has been kicked from #example by Op (plzdiekthxbye)
* Op has banned *llama*@*
* llama has been kicked from #example by Op (plzdiekthxbye)