Too lazy; didn't google. A frank admission of laziness, indicating that you expect your audience to answer your question using their own knowledge, or to google it for you if they do not already know.
Most importantly, it is a rule of the internet that if you use the tl;dg acronym after a question, your audience is not allowed to counter with a lmgtfy link or ask whether you have ever heard of google.
<nirgle> what does MSM mean in slashdot comments, tl;dg
<chondrite> mainstream media
<nirgle> ah, thanks