OP = Original Poster OR Original Post (as in the thread starter/first post). OP is also used for overpowered, depending on context. LFG = Looking for group, common MMO term LFM = Looking for more, what people who have started a group and just need more players usually use - typically with a number, like LF2M etc. PUG = Pick up group, a group made up by people who don't know eachother. FOTM = Flavor of the month, what people call the subclass/spec that is the strongest in the current meta. I guess you could refer to weapons as fotm too. WTS = Wants to sell WTB = wants to buy (both wtb and wts are common terms in trade channels, or general chat since people dont have the decency to type in the right channel) etc etc.,...

You seem like you aren't going to be a douche if i ask, so what's RNG?

Random number generator.