I did a Google search and found a couple of acronym dictionaries. One claimed to have over 4,000,000 entries, enough to boggle anyone's mind. I looked at another dictionary and found that one that stumped me, "NOS" had a total of 36 different meanings including the one that was pertinent to that thread.
Now there are a whole list of common acronyms, or short-hand abbreviations that are used in chat rooms and boards, and now used for text-messaging. But there are a whole passel of others that could really mean just about anything in some situations.
When I write one of my newspaper articles, if I use an abbreviation of any kind, I usually define it upon first use, that is common practice in journalism, and just good common sense if you want someone to understand what you're saying. In today's world, I guess it is assumed that the people you are talking to will understand this language, and sometimes it's used to hide what you're saying from others. A good example of that is when your kids will be in a chat room and you'll be watching what they're typing but won't have a clue as to what they're saying. Spy stuff if you will...